Relevant wikipedia link. The keyword is something like "many-body wavefunction."
But seriously, if you're curious, try to find a textbook online, or a series of video lectures for an introductory course (you might either watch the whole course, or skip to what you want to learn and then try and figure out what the prerequisites are, then do the same thing for the prerequisites).
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.