Easter Sunday has become a day of celebration for millions of people worldwide. Here's what to know about the Christian holiday's origin.

Christians around the world are celebrating Easter. All Christians, from Orthodox and Western churches, are observing the holiday on the same day this year - not often the case because the churches use different calendars.

As with any religious holiday observed by such a wide variety of cultures, Easter celebrations come in many forms — although all focus on the crucifixion and resurrection story that is central to the Christian faith.