Easter Monday is always the day after Easter Sunday and is a day of remembrance of Christ's resurrection.
Celebration\ Observance
People will often take part in Easter egg hunts and gift chocolate eggs to family members. For many this is the end of a 4 day weekend where they return from a short vacation trip camping or to the beach.
History
This day traditionally was a bad luck day and referred to as Black Monday but more recently it has changed to a day to relax and take part in Easter related activities.