Okay kiddo, so you know how some movies or TV shows sometimes look like they're moving kind of jerky? That's called judder. It happens when the frame rate of the video doesn't match up perfectly with the frame rate of your TV.
Now, telecine is a fancy word for the process of transferring a movie from film onto a video format. When they do this, they have to convert the old film frame rate into the new video frame rate.
But sometimes they don't get it exactly right. So when you watch the movie on your TV, it can cause judder because the frames aren't lining up perfectly. It's like when you're trying to fit puzzle pieces together, but they're just a little bit too big or too small.
It's kind of annoying when it happens, but luckily there are some special technologies and fancy TVs that can help fix it so you can enjoy your movie or show without any judder.