I do not think you can really learn what these symbols mean by reading about them. I think the best way to learn about these symbols is that study the branch of math which uses them.

Here are some:

http://en.wikipedia.org/wiki/Mathematical_symbols

Caution, eventhough this website explains these symbols it does not mean you will understand them all. Because just like I said the best (perhaps only) way to learn about these symbols is to study the branch of math which uses them.