Christianity is the largest religion with over 2.4 billion followers. They have a few religious festivals, and nearly all of us celebrate them in some way, whether we are Christian or not.
Origins
The Christian religion started over 2000 years ago. Below is an image of what Jesus Christ could have looked like as a man:
The birth of Jesus Christ
Below is a video explaining about the Nativity story:
The primary language for the video is English, but subtitles are available for other languages.
If your school or server blocks YouTube, here is the video below (no subtitles):