Well, 20 years ago, the Pirate King (basically the best pirate captain) was executed. But before he was, he said that he hid the fortunes that he stole (called One Piece) at the Grand Line. After that, all kinds of people became pirates to try to find One Piece, marking the start of the "Age of Pirates". 20 years later, a young guy starts off on his own dream of becoming the king of pirates. This guy is named Luffy and he has the amazing power of a rubber body. Earlier in his life, he ate one of the "Devil's Fruit" (fruit which gives you a random superpower) so now he can stretch his body to crazy porportions. The story is about him and his crew (crew names below)
and their search for One Piece.