From MoodleDocs

Authentication is the process of allowing a user to log in to a Moodle site with a username and password.

Authentication plugins

Moodle provides a number of ways of managing authentication, called authentication plugins.

Standard authentication plugins are:

There are also many additional authentication plugins in the Moodle plugins directory. New feature
in Moodle 4.3!

Multi-factor authentication can be enabled and managed from Site administration > Plugins > Admin tools in order to increase site security by requiring additional steps before users can log in.

See also