system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 : What are the differences between normal MP3 and VBR MP3?
gpt
the bitrate, or quality, is constant in a regular MP3.

In a VBR MP3 (Variable Bit Rate) the quality of the sound drops considerably during portions of silence or simple sound and rises during more complex sounds to reduce the size of the file, while allowing for high quality.