What is "whatis"

whatis searches a set of database files containing short descriptions of system commands for keywords and displays the result on the standard output. Only complete word matches are displayed. The whatis command is commonly found on Unix-like operating systems. The whatis database is created using the command makewhatis. Closely related commands include apropos and man.

Sample output:

$ whatis whatis whatis(1) - search the whatis database for complete words

Category:Unix user management and support-related utilities