Jiraiya was said to be a great warrior, he and Tsunade we're in love (i can't remember if they had a relation or not), Orochimaru was one of Jiraiya's students, Orochimaru somehow gained power of a white snake, Orochimaru decided to take out Jiraiya,
Jiraiya, Tsunade and Orochimaru began with fighting.
finally they used their magic of summoning a giant frog (in naruto: Gamabunta), a snail (in naruto: forgot the name lol) and as last a giant snake(in naruto: Manda).
a note: Orochimaru's name has nothing to do with the 8th bijuu called Yamato no Orochi, although Orochimaru has a Kusanagi, which is the weapon the 8th bijuu used to attack the kyuubi no yoko. Orochimaru just refers to snake, because of the orochi part.