Okay, so you know how when you take a picture with a camera and it turns out blurry? Well, the same thing can happen with the pictures and videos you see on your TV. It's called HDTV blur.
Basically, HDTV (which stands for High Definition Television) is supposed to show you really clear and detailed pictures. But sometimes, when things are moving quickly on the screen, your TV might not be able to keep up. So, instead of showing you one smooth picture, it might show you a few blurry pictures in a row.
This can happen for different reasons. Sometimes, it's because the TV doesn't have a fast "refresh rate," which means it can't show you new pictures quickly enough. Other times, it's because the video content itself isn't high quality or wasn't made for HDTV.
So, to sum it up, HDTV blur is when the pictures and videos on your TV aren't as clear as they should be because they might be blurry or choppy.