Every check should have a “manual page” with a short explanation.
(a plugin may yield one or more checks)
In WATO, there’s a section for all the check plugins that you can browse and search:
https://SERVER/SITE/wato.py?folder=&mode=check_plugins
This catalog of check plugins gives you a complete listing of all plugins that are shipped with your Check_MK installation. It also allows you to access the rule sets for configuring the parameters of the checks and to manually create services in case you cannot or do not want to rely on the automatic service discovery.