A lot of basic questions about this game can be answered here:

http://classic.battle.net/diablo2exp/

Sadly it hasn't been updated for D2R, but I have had this bookmarked for a decade+ and use it constantly for things like checking armor defense, max sockets, base damage, cube recipes, etc.

i dont think anyone has forgotten about arreat summit my friend

I think a lot of people never knew about it to forget

Lots of people don't even know who Deckard Cain is.

I think he's a guitarist or something, right?

Rapper.