Tsunade is former teammates with Jiraiya and Orochimaru and also a former student of the Third Hokage. Aka the granddaughter of the First Hokage and grandniece of the Second Hokage, many characters in the series refer to her with the Japanese honorific of "hime" (princess).
She is also known as one of the Sannins with Jiraiya and Orochimaru.

Abilities:
She is a talented medical ninja and can heal injuries that most others would consider incurable. Her healing abilities are such that she has devised a method of Mitotic regeneration for herself, making her all but invincible in battle, though using it greatly shortens her overall lifespan.
She also appears to have superhuman strength that allows her to reduce buildings to rubble.

Source:Wikipedia