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the problem with quantum mechanics is that we cannot directly observe what is going on (and the instruments we use to do the observations are also subject to quantum mechanics effects), so to explain certain phenomena we have come up with different theories that approximate what is going on. These theories work for certain cases but nobody has come up with a comprehensive theory that can be experimentally tested and works for all cases.

Here is a few books you can read on the subject. They do a pretty good job on describing what the issue is and what the interpretations mean:

Max Tegmark - Our Mathematical Universe

Sean M. Carroll - Something Deeply Hidden

Adam Becker - What is real?

Here are some things you can google if you want to just skim the subject: Wave–particle duality, The Measurement Problem, Quantum decoherence, Copenhagen interpretation, Bell's theorem, Superdeterminism, Many-worlds interpretation, Ghirardi–Rimini–Weber theory (GRW).

Last but not least, look at the Wolfram Physics Project. (https://wolframphysics.org). The take on quantum mechanics if you go along with the idea of hyper-graph is fascinating (to me)