When you watch this series, you will be confused. The anime picks up in the middle of a long-running manga series in Japan. And while the introduction gives you an idea of the background for the story, you are more or less left in the dark as to who the people are, their purpose, the struggle, etc. Each introduction is different and adds more to the background of the series as each show progresses.
But do not let this discourage you. The story telling is pretty well told. The characters get a little over the top at times, but maintain a level of realism that works, and if anything, they add a sense of humor to an otherwise bloody crusade that the main characters are pursuing.
Brought to you by the same creators of "Fist of the North Star," "Jojo's" features a unique assortment of characters (including a dog) with super powers. The powers, without spoiling the show, are alter egos of the characters, metaphysical extensions of the person using them which can be manifested to do battle for the character. These alter egos are represented of tarot cards, as well.
So the background are men on a crusade to locate and destroy an evil being with the same powers as them. The humor comes from some of the confrontations of these super powerful men, in a good way, and after the second episode, you will come to greatly enjoy the series and wish for more.