If you've never played DotA, also known as Defense of the Ancients, trying to figure out how it all works can be confusing. This is especially true if you're hopping in with people who've been playing for years and have a fondness for lashing out at those less knowledgeable. It's a game type that grew out of Blizzard's Warcraft III community and has enjoyed widespread popularity since, spurring other developers to produce their own versions like Riot Games' League of Legends. Now that Valve's making a sequel, I think it's safe to say the spotlight on the sub-genre will be brighter than ever.
To prevent confusion over capitalization, I'm just going to write Dota for the rest of the article. According to Valve's senior project manager Erik Johnson, "When people talk about DotA they say Dota. It's kind of a word, at this point. For us it's just a word, or a brand name."