WoW Client is a conceptual game term which means: the software installed and run by a player on the player's device to play the WoW game.
Description[]
This term comes from a the historical types network communication models, such as Peer to Peer, Client Server. For WoW, the game works primarily on a Client-Server model, where the user 'client' talks over a network to a game 'server(s)', with responsibility split between them for managing the users running instance of the game.