There are two types of Jokers used in rummy card games - printed and wild. Printed jokers are readily available in a standard deck. Whereas wild jokers are randomly selected cards at the beginning of the game. For instance, if 8&c is selected, then 8s from all other suits become the wild Jokers of that game.
Each Joker can represent any color and any number. Jokers can be used in groups and runs, and both jokers can be used in a single group or run. Once a Joker is on the mat, players can replace it with a suitable tile from the mat or from their rack. This frees the Joker for the player to use during the same turn.