Jesus died on a cross on the day we celebrate as "Good Friday".  On the third day, Sunday, he was resurrected (he was made alive again and came out of his grave).  This is the day we call Easter. It is the most important and oldest festival of the Christian Church, celebrating the resurrection of Jesus Christ and held (in the Western Church) between March 21 and April 25, on the first Sunday after the first full moon following the northern spring equinox.

The word, Easter, is based on the Old English name for the month of April.  The symbols of Easter in popular culture have religious meanings and are good reminders of the joy we have because Jesus is alive.