Easter .. why christian celebrate it ?

HISTORY
Easter, the Sunday of the Resurrection, Pascha, or Resurrection Day, is the most important religious feast of the Christian liturgical year, observed at some point between late March and late April each year (early April to early May in Eastern Christianity). It celebrates the resurrection of Jesus, which his followers believe occurred on the third day after his death by crucifixion some time in the period AD 27 to 33 (see Good Friday).
Easter also refers to the season of the church year, lasting for fifty days, from Easter Sunday through Pentecost; and, in the Roman Catholic Church, to the eight-day feast beginning on Easter Day called the Octave of Easter.

ETYMOLOGY
In most languages of Christian societies, other than English, German and some Slavic languages, the holiday’s name is derived from Pesach, the Hebrew name of Passover, a Jewish holiday to which the Christian Easter is intimately linked. Easter depends on Passover not only for much of its symbolic meaning but also for its position in the calendar; the Last Supper shared by Jesus and his disciples before his crucifixion is generally thought of as a Passover Seder, based on the chronology in the Gospels. Some, however, interpreting “Passover” in John 18:28 as a single meal and not a seven-day festival, interpret the Gospel of John as differing from the Synoptic Gospels by placing Christ’s death at the time of the slaughter of the Passover lambs, which would put the Last Supper slightly before Passover, on 14 Nisan of the Bible’s Hebrew calendar. According to the Catholic Encyclopedia, “In fact, the Jewish feast was taken over into the Christian Easter celebration.”
The English and German names, “Easter” and “Ostern,” are not etymologically derived from Pesach and according to the 8th century Christian monk and historian Bede are instead related to ancient name for the Anglo Saxon goddess, Eostre, who was celebrated during Eosturmonath, equivalent to April/Aprilis Bede wrote in Latin:
“Eosturmonath, qui nunc paschalis mensis interpretatur, quondam a dea illorum quae Eostre vocabatur et cui in illo festa celebrabant nomen habuit.”
Translated: “Eosturmonath, which is now interpreted as the paschal month, was formerly named after the goddess Eostre, and has given its name to the festival.”
In most Slavic languages, the name for Easter either means Great Day or Great Night. For example Wielkanoc and Velikonoce mean Great Night or Great Nights in Polish and Czech, respectively. Великдень (Vělikděn’) and Вялікдзень (Vjalikdzěn’) mean ‘The Great Day’ in Ukrainian and Bulgarian respectively.