To compare is to look at two things and see how they are similar and different.
People compare all the time. If you look at two products and compare prices, you're looking for the better bargain. It is hard to compare who was the better athlete, Michael Jordan or Billie Jean King, because they played different sports. At a museum, you can compare different paintings. If you like your math teacher better than your history teacher, you're comparing the two. If a TV shows is bad, you could say "it doesn't compare" to your favorite show.