There is reality, and there is your perception of reality. Reality just is, and it's not flexible; it always is the way it is, no matter how it evolves, and no matter how you perceive it. Your perception of reality on the other hand is malleable, because you can't ever know everything there is to know about reality, and information you find about it may be flawed or even totally wrong. The best you can have (and science works with this in mind) is a model of reality that is close enough to reality itself that it works well enough in practice. If your model of reality is too flawed, you'll eventually be facing consequences (if you take your children to an exorcist instead of a doctor, and they end up dying).
This is also why science works in reverse: they don't try to prove things, they try to disprove them. You posit a hypothesis, and then try to blow holes in it. Put simply, if you can disprove it, then it's likely wrong; if not, then it's likely correct to the degree you understand it. In math they can prove things because math is absolute. 2+2 is always 4. And math is indeed something we came up with, but so far it seems to works quite flawlessly (to the best of my knowledge). Well, philosophically, 2+2 might be 22, or a pepin, but mathematically it's really always 4.
Con artists, advertisers, politicians, and many other people take advantage of our perception of reality in some way. Some in dishonest ways, some even unknowingly. The best you can do is investigate for yourself, and try to corroborate information, or find people who know more about the subject to do that for you (I rely on some youtubers) and give you back their assessment of it, and learn to detect whether they're being coherent or not (learn about fallacies, get a bit of an understanding of the scientific method and compare to pseudoscience (a synonym of fraud, if you ask me). There are probably other useful things to know, but I could only think of those).
Not many things can be proven to an absolute degree (though facts are facts), but everything that isn't real can be disproved to the point at which anyone defending it will only be stubbornly clinging to fallacies (the Argument From Ignorance, for example). Most stuff that is real or true can be easily backed up by at least an objective argument, or at least one piece of evidence. The only obstacle to how easy it is, is usually people who profit from, or have some vested interest in muddying the waters (and they usually resort to fallacies or sophisms all the way).
Some perhaps useful links:
https://en.wikipedia.org/wiki/List_of_fallacies
https://en.wikipedia.org/wiki/Pseudoscience
https://en.wikipedia.org/wiki/Scientific_method