DotA is the short form for Defense of the Ancients which is an action real-time strategy mod built on the Warcraft III: Frozen Throne video game.
Defense of the Ancients pits two teams of players against each other: the Sentinel and the Scourge each of whom has a base. Each base is defended by towers and waves of units which guard the main paths leading to their base. In the center of each base is the Ancient which has to be destroyed in order to win the game.
Each human player is given the control of a Hero, a special unit with unique abilities (which they can choose from a hero pool of over 100+Heros) using which they will have to advance through the game. Numerous number of Items are available for purchasing in the game which will make their characters more powerful.
The enemy units (creeps / enemy heroes) can be slayed in the game in order to gain experience and gold. Gaining of experience will eventually lead to leveling up of your Hero which will allow you to unlock more abilities. The gold will help you in forging your items.
Here are links to all the info you'd need to start playing Dota
Guides : This is where you'll find all you Guides to hero's
Replays : Where you can find all the latest Professional Replays
GetDota: Where you can find the latest DotA map as it comes out
You can appreciate why with over 100 hero's to choose from I don't go into much detail about each hero. But if you're interested and wanto go look at all the heros and their stats then clicky