Side Chaining is hard.. but think of it like this......

Imagine a bloke on radio with his finger on the vol control...... He needs to make sure when he speaks, he needs to turn the music down.. And then quickly turn it back up when he's finished... So he would normally do that via the vol control with his hand....

But there's an easier way...

If you set a side chain to turn that music down via a compressor, then wow. You basically feed your voice into the side chain input and then your voice kicks the comp into action, turning the music down when you speak.... (And you obviously need to put the right values in to make sure the comp works right - but let's keep those setting for another tutorial).

But think about this... think about it not as a radio vocal scenario, but as a kick trying to keep the rest of the track down... or a kick keeping the bass-line down... or whatever you fancy....

This is sidechaining and it's a great thing to do. If you think of the radio scenario, it becomes very easy imho..... Just apply it to anything you want to do in sound.. Good luck!!!!