She is the Germanic Goddess of Spring. She is attested solely by Bede in his 8th-century work The Reckoning of Time, where he states that during Ēosturmōnaþ (the equivalent of April), pagan Anglo-Saxons had held feasts in Ēostre’s honor called Eosturmonath. However, Bede is our only source for the historical Eostre. There are no other mentions of the goddess prior to that.
However, as Europe converted to Christianity, the tradition of Eosturmonath died out. It was replaced by the Christian Paschal month, a celebration of the resurrection of Jesus (Easter).
Her festival of Ostara is celebrated by pagans on the Vernal Equinox, usually around March 21st, the first day of Spring. She is connected with renewal and fertility. Eggs and rabbits are sacred to her, as is the full moon.