Silk pillow cases are really useful to people with curly and coilled hair! Cotton pillow cases makes that kind of hair super frizzy, but a silk case can be softer on the hair meaning your curls are still intact in the morning :) Often people will use a silk wrap or hear wear instead of a silk pillow as they can ve cheaper and keep your hair more secure. It’s personal preference but can really help reduce frizz! Hope that helps

Edit: bloody spelling