whatis - Summarizes commands
whatis command…
whatis -m [ -q ]
Whatis looks up one or more commands in its database and gives the Name line taken from the manual section. The man command can be used to get more information. If * is given as the first argument, whatis displays the entire database.
The -m form causes whatis to make a new database. This is necessary whenever manual entries are added or removed. If the optional -q option is included, whatis is quiet while making the database — no output is displayed.