Hello and welcome to DOTA 2! Sequel to Defense of the Ancients: All-Stars, DOTA 2 has a prime lineage of moba awesomeness.
"What is DOTA?", you ask, eyes filled with tentative wonder. Well...
DOTA is a fast paced strategy action game....thing. You kill dudes, get gold, gain exp, all so you can kill more dudes with the eventual goal of killing your opponents Ancient and winning the game.
Here's a guide so I don't have to regurgitate shit and make this op a billion pages long: