Video Games Encyclopedia

An action role-playing game (often abbreviated action RPG or ARPG) is a video game genre that combines core elements from both the action game and role-playing game genres.
Action role-playing games emphasize real-time combat where the player that challenge a player’s physical coordination or reaction time, as opposed to turn or menu-based combat. These games often use action game combat systems similar to hack and slash or shooter games. Action role-playing games and action-adventure games differ as the former include role-playing game mechanics like player driven characters creation, decision-making regarding player character development, skill trees, or direct control over a customizable team of game characters, usually called a party. The player character’s stats determine relative strength, effectiveness or abilities and can increase when a character gains a level. MMORPGs with real-time combat systems are also ARPGs.

Reference: Wikipedia