Sidechain compression is when you have two sounds linked, and one sound is being muted by the other sound.
For example when you side chain the melody to the kickdrum, when the kick drum is played the melody will be muted slightly. (depending on the compressor threshold and ratio settings)
What is the Difference?
If the audio compressor has a slow reaction time and high threshold, this can cause heavy compression.
If the audio compression has a fast reaction time and a small threshold, this can make light compression.
What is the Best Sidechain Compression Tip?
Light side chain compression is the preferred audio compression method with professional audio engineers.