Server (computing)

A server (also often referred to as a host)...

Test
The test server is where the Public Test Realm takes place. It is used for trying out features that are in development for the next patch.

Alpha/Beta
The Alpha/Beta server is used for the alpha and beta of World of Warcraft.

Developer
The Developer server is used for internal testing.

Vendor
The Vendor server is probably used for marketing purposes. The first appearance of this server was during the Battle for Azeroth alpha testing.