You know what you want to do, but you are not sure what the command line command is that you should use. This is where the apropos command may help. While the man command gives you the details of a command, apropos searches the descriptions of all of the commands for the keyword used (in the example image above I used ‘apropos disk’ to obtain the list shown) and gives you a list of all commands that contain that keyword.
The macOS man page for apropos says:
apropos searches a set of database files containing short descriptions of system commands for keywords and displays the result on the standard output.
To learn a lot more about how to use apropos, take a look at “Linux apropos Command Tutorial for Beginners (5 Examples)“. Yes, this is a Linux article, but the top command as implemented on macOS is fundamentally the same.