Science is Testable
I want to have a brief discussion about the terms hypothesis, theory and law.
A hypothesis is a guess (presumably educated) about some scenario. The job of science is to test hypotheses (the plural form of hypothesis). That means a hypothesis needs to be testable to be a scientific one. As an example, the statement "I predict that on impact the rock will fragment into hexagonal crystals" is a scientific one since you can observe the outcome of the impact and look for hexagonal crystals.
On the other hand, the statement "The universe sits between the humps on the back of a celestial camel" is not. You might think we could look for the camel, but the universe is by definition all that physically exists. So sitting on the back of something else beyond the universe isn't testable. Laws of physics relating to space and gravity tell us that it would be impossible even in principle to probe regions outside the universe. It truly is a closed box in that sense. If we did find new regions of our universe, they would simply become a part of our universe, by definition.
Once a hypothesis has been tested and refined sufficiently such that it confirms the outcomes of experiments time and again, the hypothesis graduates and becomes a theory. In the scientific use, the word theory is not just a random idea someone has about something. Rather, it is assumed to be the best explanation we have on a topic that's been tried and tested. It is nothing like when someone says "I have a theory about why she behaves that way."
When comparing competing theories, it may be possible that two theories offer equivalent predictive powers and therefore appear equally valid. The notion of Occam's razor is often employed to choose the preferred theory. The idea is that the simpler explanation is preferred since it is often more easily tested and verified. See this link.
A law is a bit different than a theory. It's more of a general term for a relationship among things or behavior of a system. We speak of the law of gravity, or the laws of thermodynamics or conservation laws.
While certain topics are called laws and others theories, I wouldn't really fault you for calling a theory a law or vice versa. In general the laws are the simpler or more general relationships and theories more complex and mathematical, but that rule can fail. There is nothing really fundamentally different about Newton's laws of motion and quantum theory, for instance.
On top of that, physicists additionally use the term "effect", as in the Doppler effect or the Casimir effect. They also use the term "principle", as in the causality principle, or correspondence principle or Fermat's principle. Effects in this sense are like theories, but perhaps can be thought as describing isolated topics rather than more general areas of study. Principles are concepts which can usually be summarized briefly using written language.
The reality is that we use many terms that mean nearly the same things, and you just have to know which one to use based on experience. The important thing to take away is that unless we call something a hypothesis, the concept or idea should have been tested and re-tested countless times.
On the other hand, I have not ever in all my years in graduate school or afterwards had a colleague use the term hypothesis as we defined above and learned about in middle school, when referring to their own work or that of others. All sorts of unconfirmed and untested "theories" are instead flying around out there when the label "hypothesis" would have been more appropriate. As an example, by typing "theory suggests" into Google, this was the first link: "Testable theory suggests information has mass and could account for universe’s dark matter." It's good that it's testable so that it can be called science, but it HAS NOT YET BEEN TESTED! That makes it a hypothesis, and an interesting one at that, but certainly does not qualify it as a theory.
Science is Testable?
We need to discuss the testability of scientific hypotheses and theories. There are gray areas here. Everybody agrees that if it's not testable, it's not science. The trouble is that some of the biggest theories are hardly testable in the way that most people understand testable.
It's easy to test relativity theory (in many cases), or to test quantum theory. It may take expensive or sophisticated equipment, but such experiments are routinely done and those theories stand up to careful scrutiny.
But what about the big bang theory or the theory of evolution from biology? We don't have labs big enough or energy densities great enough to create new universes, so the big bang is hard to test. Besides that, the big bang is not a simple process. It includes aspects of the physics of the most energy-dense, exotic forms ever studied, the structure of spacetime, particle physics, stellar formation and evolution, etc.
There are parts of the big bang theory that are still completely unanswered. One such aspect is called inflation. Two others mysteries are the seemingly requisite existence of dark energy and dark matter about which we know nothing. The first moments are also unexplored territory. Thus, we should understand that all scientific theories have not been, and in many cases cannot be tested and validated. This is troubling, and suggests the use of the term "hypothesis" instead, yet it isn't.
We have to understand that with big "theories" like these, we do our best to test the parts we can, and then decide whether the proposed chain of events matches existing computer simulations and observational data. The big bang, in this sense, is more like a hybrid of truly testable scientific theories and some hypotheses. According to most astrophysicists, it is the best model or theory of the chain of events we have at the present time to describe the formation of our universe. There is no doubt that parts of it will evolve over time and details will be modified or filled in. The act of perfecting such a model or theory is exactly the role of science.
The theory of evolution from biology comes to mind as the hardest of all theories to validate. We are told that life is a product of chance and time. This has been professed since 1859 with the publication of Darwin's On the Origin of Species. The theory of evolution is a good example of the practice of naming a process (or long series of them) and laying out a basic roadmap of events, and thereby proclaiming understanding. There is no more complicated process in nature than life, its formation, its interaction with the environment and its procreation.
Having seen the complexity of life's molecules at a level not possible to see without a physics lens, I was awestruck. For this reason I was not terribly surprised to read recently that the example used more than any other to exemplify evolution - the finch beaks on the Galapagos islands - has recently been shown to be potentially incorrect. Rather, the finch beaks are likely epigenetic variations. Epigenetic variations are variations of the expression of already-existing genes. The article suggests that the finches had the ability to alter beak size and shape already in their genomes, and environmental changes caused the expression of different parts of their existing genomes to occur. Here is a link to a research paper on the topic. Epigenetics is a fascinating topic only recently making its way into biology textbooks even though it's been well recognized in research circles for decades.
Evolution of the usual variety surely occurs, as in the case of virus mutations. But the genome is now understood to be way more complex than previously believed. DNA has multiple layers of information besides the basic sequence of nucleotides - the epigenome perhaps being the most interesting of them. This presents two challenges for present evolutionary theories: 1) To actually look into whether such epigenetic gene expression variations that are heritable have been erroneously called random mutation and natural selection, and 2) If not, to provide an explanation for DNA's even more complex structure than previously thought as a consequence of randomness. Outside of the case of evolution, the creation of complexity from randomness is not recognized in science nor seen in natural law.
When it comes to any theory, it's appropriate to take the individual parts and claims, and assess the data for each in turn. I expect that Darwinian evolution will in the upcoming decades itself be found to evolve. This is not a bad thing. This is the point of science. Danger to progress and real understanding arises when we too strongly embrace our current theories. Science itself is meant to be an evolutionary process.
Regardless whether something is called a theory or not, as educated people we need to understand the concepts involved, the assumptions made, and the extent to which they've been validated before we should accept or reject any theories. Ask questions. Think things through. Make your own determinations after you have what you feel is sufficient data. The history of science is replete with examples of people asking the tough questions or questioning the status quo before making a major discovery or overturning an old paradigm.
To me this makes science fun. It isn't just about accepting dictated truth. Science is a process of curious inquiry leading to continual improvement. It is much like play in this sense. I recommend maintaining your curiosity, your humility, and a healthy level of skepticism at all times.
One last note: I had a student once who was resistant to learning anything I had to teach him. After a few weeks (once I recognized this) we had a long discussion. It turned out he didn't want to learn physics because he thought he'd get indoctrinated into a false paradigm, or way of seeing the world. He was skeptical, but to a degree that stunted his education. I pointed out to him that for him to come up with better scientific theories and concepts, he'd need to know where the present ones fail. I suggested to him (and also to you) that you learn what we presently know as a starting point to progress. I will do my best to point out limitations in our present theories and knowledge so that I don't mislead you deliberately. Only after having acquired understanding of the current state of science will you be equipped to advance it and potentially fix present theories or inadequacies.