Easter is an English word, adopted from the Anglo-Saxon pagan festival of Eostre. Most languages, conversely, are derived from the Greek or Latin Pascha, which clearly reveals the link between the Christian festival as the Paschal Feast and the Jewish Pesach or Passover.
For Christians, Pascha or Easter is the time when Jesus was crucified and rose again. These events occurred during the Jewish festival of Passover.
The First Council of Nicaea in AD 325 established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the March equinox. The Eastern churches still follow the Julian calendar (as opposed to the Gregorian calendar), which causes Pascha to co-incide more readily with the Jewish Passover. For details on the Biblical dating of Passover, see Festivals in our Jewish section.
Pascha is usually celebrated as follows:
The ‘Holy Week’ of Easter begins on the Sunday one week prior to Easter, commemorating Jesus’ triumphal entry into Jerusalem on a colt, the foal of a donkey, and refers to the palm leaves that the crowd laid down on the road before Him. Traditionally, some churches parade through their towns and villages with a donkey on Palm Sunday.
Most traditions celebrate Good Friday and Easter Day, but additionally there is Holy Monday, Tuesday and Wednesday (to which there are no specific traditions attached), Maundy Thursday, and Holy Saturday. Additionally, some countries have a secular bank holiday on the Monday after Easter Sunday.
Maundy is derived from a Latin word denoting the washing of feet, and commemorates the ‘Last Supper’ or Passover Meal of Jesus and his disciples in the upper room in Jerusalem at which the Master became a servant and washed His disciples’ feet.
Friday is the traditional date of the crucifixion, due to the reference in the gospel of ‘before the sabbath’ but this sabbath could have been the High Sabbath of Passover itself rather than the weekly sabbath, making the crucifixion on the Wednesday or Thursday, allowing for a full three days in the grave. Day and Hour. (Confusingly, in Judaism the High Sabbath (Shabbat haGadol) is the Saturday before Passover, rather than the day of Passover itself, which nevertheless is a sabbath even when it is midweek.)
Also known as the High Sabbath, Black Saturday or Easter Eve, this is the day (the only full day in the traditional dating and counting of Easter) in which Christ lay in the tomb. Some churches are left open and empty on this day. Holy Saturday at Wikipedia.
After the weekly sabbath ended, Jesus rose from the dead. Interestingly the Roman Catholic liturgy for Easter Day begins at sunset on Holy Saturday, in reference to the fact that Jewish days begin and end at sunset. cf Firstfruits.