Ostara is celebrated on or about March 21, celebrating the Spring Equinox
Ostara is one of the eight Sabbats of Wicca (also known as celebrations, rituals,holidays), that make up the Wheel of the Year.
Ostara is derived from ancient Spring Celebrations, mostly from European regions., honoring the Goddess as the Spring Maiden and the Horned God, metaphors or symbols of the warming Spring with all of it's new life and new beginnings.
Ostara is a modern word derived from the old Norse fertility goddess Eostre symbolizing new beginnings. As a Goddess of Spring, she gives power to the growing vegitation (especially crops and flowers) and growing fertility of Earth and all it's creatures. The Horned God, also known as the old God, Pan, Cern, Cernnunos, symbolically joins us in the celebration of nature. He has come into the beginnings of His fertility and he feels the first longing for the Maiden.
The word 'Easter' also comes from the Norse Goddess Eostre.
Symbols of Ostara are alm almost identical to modern Easter: decorated eggs, rabbits (the Easter Bunny), Spring flowers, etc..
Eggs and rabbits are obvious symbols of fertility, fitting perfetly with the Spring, the Maiden Goddess and the Young God of the Wild.
Some Wiccan traditions do not perform any magick at Sabbats, using them only for Celegrating the Turning of the Wheel, the season and the God and Goddess. Other Wiccan traditions use these times for spellwork associated with the symbols and purpose of the Sabbat. For Ostara, that would be spells to attract abundance, prosperity, fertility, etc.