can some1 explain how a knot happens- IM TO INNOCENT I DONT UNDERSTAND

Knotting in Omegaverse is based off what certain animals do irl when they mate. basically in these mangas its when the Alpha's penis enlarges when inside the Omega it 'knots' so that it can't easily be removed and gives a higher chance to successfully impregnate them (づ￣ ³￣)づ

ohhh thanks!!