Basically speaking, compression realizes the function of automatically turning down the volume of your music when the volume of your music increases sharply. This is how all compression works. Compression is often misunderstood, and the reason why it causes confusion in terms of function is often because of the circuit design inside the effector. Compression often produces some changes in the tone that you like or dislike when controlling the volume. Another reason is that it's actually very difficult to get the compression set up so that your signal is compressed enough, but not too much.