Simplify the following text for a Grade 6 native English-speaking person.
Original: This includes elongated coins , encased coins , souvenir medallions , tags , badges , counterstamped coins , wooden nickels , credit cards , and other similar items . It is related to numismatics proper ( concerned with coins which have been legal tender ) , and many coin collectors are also exonumists .
Simplified: Numismatics is the study and collecting of coins and the history behind the coins .