Dota wikipedia,

Defense of the Ancients (commonly known as DotA) is a custom scenario for the real-time strategy video game Warcraft III: Reign of Chaos and its expansion, Warcraft III: The Frozen Throne, based on the "Aeon of Strife" map for StarCraft. The objective of the scenario is for each team to destroy the opponents' Ancients, heavily guarded structures at opposing corners of the map. Players use powerful units known as heroes, and are assisted by allied heroes and AI-controlled fighters called "creeps". As in role-playing games, players level up their heroes and use gold to buy equipment during the mission.

• The scenario was developed with the "World Editor" of Warcraft III: Reign of Chaos, and was updated upon the release of its expansion, The Frozen Throne. There have been many variations of the original concept; the most popular being DotA Allstars, which eventually was simplified to DotA with the release of version 6.68.^[3] This specific scenario has been maintained by several authors during development, with the current publicly anonymous developer known as "IceFrog" developing the game since 2005.
• Since its original release, DotA has become a feature at several worldwide tournaments, including Blizzard Entertainment BlizzCon and the Asian World Cyber Games, as well as the Cyberathlete Amateur and CyberEvolution leagues; Gamasutra declared that DotA was perhaps the most popular "free, non-supported game mod in the world". Valve Corporation is currently developing a sequel, Dota 2.