It's basically a story about pirates!
But it's a lot more than that.... it revolves around a boy named Monkey D. Luffy, searching for the legendary One Piece on the grand line. He sails the seas, gathering comrades, crewmembers, and meets all sorts of awesome people. He also ate the devil's fruit, a fruit that contains superhuman qualities, but the person who eats it can no longer swim. (Water is his weakness, kind of like kryptonite). But the fruit gave him the power of a rubber human, so he can stretch and stuff.
But really, the most appealing aspect is the friendship aspect. It's so awesome and fun!
Please watch One Piece!