What is CrossFit?

Hi, I keep hearing and reading about this crossfit training programs and I have no idea what they are talking about. The exercises I see associated with it look like exercises I do for football so I would like to learn more about this. Can someone please explain this to me? Please help. Thanks! I didn't find the right solution from the Internet. References:https://forum.bodybuilding.com/showthread.php?t=143147123 Medical Device Marketing Video