In computing, apropos is a command to search the man page files in Unix and Unix-like operating systems.
Apropos takes its name from the French "à propos" (Latin "ad prōpositum") which means about.
The output is a list of all manual pages containing the search term (case insensitive) in their name or description.
[1] makewhatis is a command for indexing all on-disk manuals into a database that apropos and whatis can read from.
[3] The database is traditionally plain text, but man-db, the implementation found on many Linux distributions, use a Berkeley DB instead.