From Wikipedia:

A role-playing game (RPG; often roleplaying game) is a type of game in which the participants assume the roles of fictional characters and collaboratively create or follow stories. Participants determine the actions of their characters based on their characterization, and the actions succeed or fail according to a formal system of rules and guidelines. Within the rules, players can improvise freely; their choices shape the direction and outcome of the games.

Artix Entertainment specializes in the development of Flash-based RPGs. AdventureQuest, DragonFable, and MechQuest are examples of RPG games by Artix Entertainment.