Manual:Bot passwords

Bot passwords allow bots to log in with a simple username-password combination even if the wiki employs some extra authorization steps that the bot framework could not handle; they also allow limiting the permissions given to the bot (e.g. the bot might be allowed to edit articles but not to create new ones). New bot passwords can be created via Special:BotPasswords.

This is a simpler alternative to OAuth, meant for bots which do not support that. If the wiki and the bot support OAuth, use that instead; it is more secure.