Venusaur is #002 in the pokédex. It is a intresting GRASS and POISON type, and is worth training it.
Ivysaur is an intresting pokémon. When evolved from Bulbasaur, the plant on his back was growing larger. He becomes alot stronger when evolved. He doesn't have a very big role in the Anime.
Evolution chain: Bulbasaur ----> (+-lvl 16) Ivysaur ----> (+-lvl 32-36) Venusaur.