The “whatis” command is a useful tool for obtaining quick information about various Linux commands or functions. It searches through manual pages and displays short descriptions of any matched command. This command is particularly helpful for beginners or for those who want a brief explanation of a certain command. It is important to note that this command is different from the “ls” command which is used for listing files and directories. The “whatis” command finds its information from the man page of the given command, and it can also search for commands using wildcards or regular expressions. Additionally, while the “apropos” command searches through manual page names and descriptions, the “whatis” command specifically looks for command descriptions.