Short answers, pulled from the story.
Easter commemorates the resurrection of Jesus from the dead, described in the New Testament as occurring on the third day after his burial at Calvary around 30 AD. It is considered the culmination of the Passion of Jesus and one of the chief tenets of the Christian faith.
Easter is a moveable feast calculated on a lunisolar calendar rather than a fixed solar date. The First Council of Nicaea in 325 AD established that Easter falls on the first Sunday after the first full moon on or after the vernal equinox, producing a date that shifts each year.
Eastern Orthodox Christians apply the Easter calculation to the Julian calendar, where the 21st of March currently corresponds to the 3rd of April in the Gregorian calendar. The Julian calendar's lunar tables also run five days behind astronomical reality, pushing Orthodox Easter to a range of the 4th of April through the 8th of May in Gregorian terms.
The 8th-century Anglo-Saxon scholar Bede recorded in The Reckoning of Time that an Old English month corresponding to April was named after a goddess called Ēostre, in whose honor feasts were celebrated. The modern English word Easter and the German Ostern both developed from related Old English forms of that name.
The custom of the Easter egg originated in the early Christian community of Mesopotamia, who stained eggs red in memory of the blood of Christ shed at the crucifixion. For Christians, the Easter egg became a symbol of the empty tomb.
The Easter Bunny originated in Germany as a legendary anthropomorphic gift-giving figure. Children in the tradition leave out baskets to be filled overnight, and the custom spread to become widely popular in American culture, where it is compared to the role of Santa Claus.