When we were children, we called the sides of our coins "heads" and "tails." If you want to be taken seriously as a numismatist (person who studies and collects coins), it is time to learn the proper terms to describe your coins. This way, you can talk to other collectors and coin dealers in the special language of coin collecting, and they'll not only understand what you mean, but they'll have a lot more respect for you as a serious numismatist.
Have you ever seen a tail on the back of a coin? Neither have I, but most coins actually do have a head. We call the head side of the coin the obverse. The other side, (the one without the tail) is the reverse.
