These are the basic questions that you can ask your Linux box regardless of the flavor you are using and Oh, it works only when entered at the Terminal prompt.

whatis 

     will display man page header for a particular command

     syntax:

         whatis [opts] [name]

who 

     will return and display logged in users (valid onces only)

     syntax:

         who [opts] [file]

whoami 

     displays your current info

     syntax:

          whoami [opts]

whereis 

     display location of command and man page

     syntax:

           whereis [opts] [name]

which 

     show path of command.

     syntax:

          which [opts] [name]