How does the stock market work?

[Mike w]

I mean you buy a stock there has to be someone selling what if no one is selling what then? also when you do shorts and you borrow sell them and then buy them back and give them back to make profit of a drop in stock what if you cant buy anywhere them back?

I mean i can understand basic stuff (or maybe not lol) but can anyone direct me to some stuff where i can learn about the basics and maybe even more advanced stuff.

Thanks