Online multiplayer game
An online multiplayer game (OMG) is a video game that can be played over the Internet against other players. These types of games can only be played over the Internet, and must involve multiple users.
Online multiplayer games is an encapsulation of many other popular types of games. It is a master category for the likes of:
MMORPG - Massively-Multiplayer Online RPG
MMORTS - Massively-Multiplayer Real-Time Strategy
MMOFPS - Massively-Multiplayer First Person Shooter
Online multiplayer games do not have to be able to support a wide audience, but must accommodate at least two players, which is why the "Massively-Multiplayer" tag is not present in the title.
Some examples of OMGs are Hattrick, Utopia and Earth: 2025. Online multiplayer game resources are available to browse massive directories of these types of games, such as Online Multiplayer Games Network (OMGN) and Multiplayer Online Games Directory.
Multiplayer online game (MOG) is a variant expression for online multiplayer game.