kenshin is a wandering samurai that is living/staying alive to repent for all of his wrong doings in the past. he used to be an assassin and killed many people. so now he wanders around and helps people, but he always ends up fighting [but not killing] people who do wrong to others.
if you have more questions about it just ask, though you might be able to find someone else who can do a better job. overall the storyline/show is good. and if you really want to know about kenshin, you should watch the movie: "samurai x [vol. 1&2]". i think that there might be another movie that explains his story better, but i can't think of it right now.