Coins were the main currency of Club Penguin.
Basically, Club Penguin was one of the best online games to be played with friends all over the world. It was a massively multiplayer online game. It was specifically designed for children between the 6 to 14 age groups. However, people of any age group were able to play Club Penguin. The memberships were available free and paid (additional features that allowed purchasing virtual clothing, furniture, etc.) too.
Unfortunately, the game was discontinued from March 30, 2017, at 12:01 AM. However, it was succeeded by another game, Club Penguin Island, but it also failed after one year. Since then, the game has been permanently shut down.