I'm a layman, so I'll offer some layman's terms. Apologies to those well versed should I misspeak. Please correct my interpretation as needed.
The wave function describes all possible states of an object. This is really the heart of the whole "Schroedinger's Cat" issue. Let's say you put a cat into a box. In that box is a poison in a glass vile, and the box gets dropped (I've changed the real thing a bit, but this is close).
So, cat in box, glass vile of poison in box with cat, box gets dropped. This is where we are.
So, the wave function which describes this discusses all possibilities.
The vile didn't break, and the cat is alive.
The vile did break, but the cat survived.
The vile didn't break, but the cat died (maybe he had really bad vertigo .
The vile did break, and the cat died.
Before you open the box, according to QM, the cat is actually all of these things at the same time. Since you don't know, all you have is a wave function which describes the probabilities of each state.
Here's where it gets weird though.
The cat is also anything else, just at a lower probability. The cat is a dog. The cat is your grandmother. The cat is elvis. The cat is George Washington. The cat is a pterodactyl pulling a meerkat out of a blackhole... According to probability, it's actually all of those things until it's observed, and the wave function is used to calculate the probability of each potential state... Most are just so very unlikely that they can be disregarded, and although still possible, we tend to look at the "cat is alive/cat is dead" only split.
So, once you've opened the box and you look in, you actually learn the state of the cat. You know if it's dead or alive, you know if the vile of poison broke or did not, you know if Ben Franklin wearing a ball gag was in there the whole time... and "the wave function collapses."
All of the possibilities that made up the wave function go away (hence the collapse), because you've observed the system and only one possibility was realized.
Just wait until you read about double slits. Check common sense at the door and prepare to enter the rabbit's hole.