Rainbow Pirates is kind of like playing Rummy on an enchanted island while being attacked by pirates drinking piña coladas.
The object of the game is to earn as many Treasure Points as possible by placing card groups (treasure) on your island. However, you can also attack your opponents with pirate cards (stealing or blowing up their treasure) or use them to give yourself other advantages.
The game was designed to allow for multiple strategies (ranging from guns-blazing aggressive to peace-loving non-violence) based on the player's hand, preferences, and group dynamics. (eg, attacking an opponent's island can give you the edge you need to win, but also often causes reprisals and limits the treasure you earn from Black Cards)