No surprises; tail is the opposite of head. We can use it to view the contents of a file from the bottom.

What would be the output here? 

When I'm feeling sad,
I simply remember my favorite things,
and then I don't feel so bad.
I simply remember my favorite things,
and then I don't feel so bad.

See that? While the -3 option shows the last three lines, -2 displays the last two lines of favorite_things.txt.

tail works in exactly the same way as head.