Modern video formats have been designed in such a way as to minimize the storage they take up while maximizing things like resolution and frame rate. To achieve this goal they have developed some clever techniques that can look very cool when they don’t work as they should.
Let’s start with frames. Each frame of a video is like a picture. Most videos very between 24 and 60 frames per second and as you can imagine having 60 pictures for only one second of a video would take up a huge amount of space. So what the developers of modern video formats did was only have full pictures when absolutely necessary. If you think about it a lot of the frames in a video are just a very similar picture with slight differences. So what many formats do is simply tell the old pixels on the screen where to go to make the new picture instead of creating a whole new picture. This process allows for much smaller file sizes for videos as well as allowing datamoshing.
What datamoshing does is it gets rid of the new full picture frames and instead only keeps the frames that tell the pixels where to go. What results is a new video moving based on another videos directions or an image from the same video where the pixels go in directions they’re not suppose to. This process can lead to some very cool and unique glitch effects that have been used to various degrees within different mediums to create an interesting and unique effect.
Here are some examples: