Collecting First Day Covers

This is a first day cover. It is a special envelope!

There are two 18 cents stamps in the corner of the envelope.
That kind of stamp was first issued (sold) on May 18, 1981. (Stamp catalogs tell when stamps were first issued.)

Now look at the date on the postmark. (The postmark is the markings put on by the post office. A postmark shows when the stamps were used). The postmark date is the same as the date the stamp was issued. That makes this envelope a first day cover.

The drawing on the envelope is to honor the stamp.