Practicing alone
From QWiki
Everytime you run QuakeWorld, there's the option to play by yourself, practice movement or aim, alone or against bots.
Bots
Bots replace human players. You can spawn bots in compatible KTX servers. See more Playing with bots.
But also offline. See below.
Deathmatch
Team deathmatch, FFA
Offline =
You can also play with bots offline.
Aim
Movement
versus Monsters
see Bloodfest.