Most of the major holidays have symbols or icons associated with them. Easter, perhaps, is the most iconic holiday of them all.
Easter is a time of remembrance of the crucifixion and resurrection of Jesus Christ. For many non-Christians (as well as many Christians, for that matter) it is a celebration of the advent of spring. Many Easter symbols represent new life as in the new, resurrected life of the Savior and the promise of salvation for mankind, as well as representing the re-birth of the world from cold winter days to warming springtime.
Some Easter symbols originated, not out of the event of Jesus Christ's resurrection but rather from ancient pagan symbolism. In fact, the very name Easter takes it's origins from an ancient pagan festival. Eostre or Eastre was an Anglo Saxon goddess of fertility. Each year in the month of April, festivals were held in honor of the goddess Eastre and the arrival of spring. With the rise of Christianity, missionaries thought it best to keep some of the pagan festivals and symbolisms rather than to ask the new converts to make a 360 degree change. The symbols were then adapted to coincide with Christian practices. Over the years, the springtime festival name was changed from Eastre to Easter and became connected with the celebration of Christ's resurrection.
Rabbits and hares were a symbol of fertility and abundant new life in ancient times. It is said that Eastre, goddess of fertility, had a rabbit as her constant companion, and I think we all know why a goddess of fertility would choose a rabbit for a pet. Rabbits and hares are both prolific breeders. In fact the females of some species of hares can conceive a second litter of offspring while still pregnant with the first (superfetation). Now that's what I call a fertile Myrtle!
The story is told that Eastre arrived late one spring, feeling bad about that, she decided to make amends by saving the life of a poor bird whose wings had frozen in the snow. Eastre made the bird her pet, and feeling compassion for the bird because he no longer had the ability to fly, she turned him into a snow hare and named him "Lepus". In remembrance of his life as a bird, Eastre gave Lepus a special gift. For one day a year, he was given the ability to lay eggs, and not just any old eggs, but eggs of all different colors.
The Easter Bunny
The Easter Bunny was introduced to America by German settlers who arrived in Pennsylvania Dutch country during the 1700's. The German children would each make a nest, which they believed if they were good, the "Oschter Haws" would fill with colored eggs. Over the years, the nests would eventually become Easter baskets which the Easter Bunny would fill, not only with colored eggs, but candy and trinkets as well.
Sources: Wikipedia Professor's House History.com