Easter is a Christian holiday, that goes after Lent. It is the supposed crucifixion on Good Friday and later resurrection of Jesus. Technically the actual date of the resurrection wasn't recorded but there is a strong tradition that it happened on Easter Sunday. The Roman Catholic and the Anglican creed both include, "On the third day he rose again from the dead." and the third day is assumed to be Easter Sunday.
The Easter Bunny
Some Christians see the Easter Bunny as a bastardization of Easter, because people shouldn't go duck-hunting on the most important holiday. However it's the only way (beside Santy Clause) to get kids to worship god (An editor made that up, but it's probably partially true).
There is a good and a a bad side to Christianity, see the category page