This command is used to find out information about others on the net. It
can be used to find out if someone is logged on, how long they have been
on, and if they have any unread mail. It may also give you some more
information about the person depending on whether they have a .plan
file(To create this file, use an editor to make a file named .plan. It can
contain anything. The permissions on this file must be 644--these
permissions are detailed later in this guide in the chmod section). The
finger command looks people up by their email address. The format of the
command is also dependent on "where" the person you are looking for is
located. 

If they are on a totally different machine (for example at a different
university or at a business), then you would have to type in the full
address after finger. If you wanted to finger jasha@magic.nowhere, it
would look like this: 

ux1> finger jasha@magic.nowhere

It is important to note that the finger function will not always work,
because some machines have it turned off.