What is the difference between pre-inserts and post-inserts?

What is the difference between pre-inserts and post-inserts?

I can’t see my plug-in on the post insert.

Have a look at this (amateurish) drawing.

So for some reason, on Cubase13 they’ve made it so you have to physically right click the insert and press “move to post-fader slot” instead of just leaving all the insert boxes there to do it manually in drag