In the compression world it means exactly what it says. Insufficient frame rate is one of the most noticeable video deficiencies. In addition, the missing frames will contain extremely important lip synchronization data. In other words, if the movement of a person's lips is missing due to dropped frames during capture or playback, it is impossible to match the audio correctly with the video. Symmetrical compression means that if you can play back a sequence of 640 x 480 video at 30 frames per second, then you can also capture, compress and store it at that rate.
Asymmetrical compression means just the opposite.
The degree of asymmetry is usually expressed as a ratio. Asymmetrical compression can sometimes be more elaborate and more efficient for quality and speed at playback because it uses so much more time to compress the video. This is the compression ratio and should not be confused with the asymmetry ratio. The compression ratio relates to a numerical representation of the original video in comparison to the compressed video. In comparison, the compressed video is represented by the smaller number, in this case, that is 1.