Commands whatis and apropos

TIL about the commands whatis and apropos.

apropos searches man pages for keywords

$ apropos converter
pdb2mdb(1)               - Program Database to Mono Debugging Symbol converter
CPAN::Meta::Converter(3pm) - Convert CPAN distribution metadata structures
native2ascii(1)          - native to ASCII converter

whatis shows descriptions of commands that match

$ whatis rm
rm(1), unlink(1)         - remove directory entries
git-rm(1)                - Remove files from the working tree and from the index

h/t this tweet by Peter Cooper‏