The history of online gaming includes contributions by many different companies and entities. Online gaming began as multiplayer gaming, but has evolved to include online gaming servers and massively-multiplayer online game settings.
Multiplayer games started in 1972 with PLATO.
PLATO was a joint project of the University of Illinois and Control Data Corporation, which enabled students to interact with other terminals for the purpose of education and computer-aided learning. In 1972, new interfaces enabled students to begin creating games, and the world of multiplayer gaming began.
MUD was the first network game.
MUD in 1978 spawned a genre of network-based games, enabling players on the network to interact and explore the MUD game world. MUD games ultimately paved the road for MMORPGs, with the concept of a shared world.
MAD on BITNET was the first worldwide multiplayer game.
In 1984, MAD appeared, and it was the first game to enable worldwide connectivity. MAD was a MUD accessible to anyone on the worldwide computer network, and it lasted for two years.