"Choppy" means "not smooth". The most common use of the word "choppy" is to describe water that has a lot of waves:
The water started getting choppy, so the rescue effort had to be suspended.
When you're talking about computer video, a "choppy" video is one that doesn't move smoothly. Instead, it stops in some parts to wait for the signal to catch up. You can use it in the same way for audio recordings or telephone conversations:
I don't get very good reception here, so excuse me in advance if our conversation gets a little choppy.