Have you ever wanted to watch a movie that you didn't have, but your friend had it on DVD? Well, there's this group called the DVD Copy Control Association (DVDCCA) that doesn't want people to copy movies from DVDs and share them with others. This group makes rules that prevent people from copying movies using special software or devices.
It's like when you have a toy that's only meant for you to play with, and you don't want your friends to take it and play with it too. The DVDCCA wants to protect the movies and make sure they only get shared in the ways that the movie studios approve. They are basically the grown-ups who make rules for how we can and can't use DVDs.
So, when you see those warning messages before a movie starts, telling you not to make copies or lend the DVD to others, that's because of the DVD Copy Control Association. They want to make sure the movie studios get paid and that we all follow the rules of owning and sharing movies on DVDs.