Quantum physics is pretty broad... defining it as a whole is pretty rough to do but let's cover a few basic concepts at least.
Quantum basically means a single or smallest value of something. A quantum of energy would be the smallest possible amount of energy for example. Hence, quantum physics deals with stuff on a really really small scale, though this information can have important effects on a larger scale.
Examples of this include, but are not limited to:
Defining gravity, and why it doesn't work like the other 3 known forces of nature (electromagnetics, strong nuclear and weak nuclear).
Identifying, classifying and generally trying to prove and make sense of the little bits that make up atoms that're smaller than even electrons, neutrons and protons. Anything sub-atomic gets into quantum theory.
Dealing with the fact that there seems to be odd stages in nature; whot works on a large scale doesn't work the same way on a small scale.
Most of the really weird stuffs involving probability are due to the above issue, and difficulties in measuring tiny stuff (standard equasion basically breaks down into meaning that if something's going in a really random curve, the more accurate yeu know the direction it's going, the less accurate yeu know where it exactly is at that moment, but if yeu know where it is, yeu can't tell which direction it's going; a bit more complex than that but yeah that's the basic kinda interpretation).
There's stuff related to time dialation, radiation, particle pairings, and lots of really weird things like dark matter.
If yeu want the coles notes version:
"Freaky action at a distance" ~ Einstein
Anyways, stuff works really weird because we don't really know the EXACT rules of the universe as such... normally when yeu learn something, yeu start with the basic foundation, understand that, then work upwards from there. The problem is, we don't know whot the basic foundation is, we started somewheres in the middle, because that's all we can see without insanely powerful microscopes, and some stuff we can't even prove exists outside of theory because they're so small, or aren't easy to see like dark matter.
So yeah, we're stuck starting from the middle and trying to backwards engineer the answers, except all we get basically is a button we hit that says "yes" or "no" on whether our current guess was accurate or not... problem is, it's such a complex concept most of the time that there could be thousands of things which're "close" but only one that's actually accurate.
So physics is generally accurate normally... until yeu get too accurate or large a scale; on a really tiny scale, a minor error is very large in comparison to the whole; ifs yeu have 100 and are off by 1, no big deal only 1% error margin. If yeu have 5 and are off by 1, that's a 20% error margin and it no longer works. Same thing is true the other way around... 1 degree angle isn't that big a deal on a small scale, but go into like astronomical units of distance measurement... and 1 degree can be billions of miles difference.
As such, our 'kinda vague guesstimates' we have from trying to figure things out backwards aren't that accurate on the large nor small scales, and quantum physics kinda tries to make it more accurate on the small scale, since if yeu can get it accurate there, then it'll make the large scale more accurate as well. Usually... then again some of the stuff that happens small scale is really really freaky weird.
Seriously, yeu could practically call quantum physics magic for how strange that stuff is XD
but I guess it applies to quantum physics ass well. It's a good example.
