Delivering placenta/after birth massages

This was a comment on another post but I wanted advice on a whole seperate forum, I'd never even heard of these 'massages' until a few weeks ago and I'm 24 weeks! Agee reading what people said and how it's the worst part of having a baby I'm terrified. I don't do well with pain, I don't even get massages from professionals because they hurt my back. Can I refuse the massages? And what even is delivering the placenta? I thought it was just a small little bag that comes right out?