Info:
Introduced in the first half of the manga, Jiraiya appears as a perverted old man whom the lead character, Naruto Uzumaki, refers to as "Ero-Sennin" (エロ仙人 or "perverted sage"). It is established that he was a student of the Hidden Leaf Village's Third Hokage, and one of the Three Legendary Sannin shinobi, along with Orochimaru and Lady Tsunade.

Abilities:
Jiraiya is known as the "Toad Sage" (蝦蟇仙人). Having been trained by toads to utilize their secret arts, Jiraiya can summon them to his side as allies during battle and if need be, he can also summon parts of toads, e.g. blanketing an area with a toad's esophagus to immobilize and trap an opponent.
In the second half of the series, Jiraiya is shown to possess a number of toad-based abilities not wholly reliant on summoning. Most prominent of these is being able to enter the "Sage Mode" (仙人モード), a transformation that drastically increases his physical abilities and the strength of his attacks.

Source:WIkipedia