We have 2 kind of wigs are mono wig and full lace wig.
Mono wig is usually made with a cap construction that has a skin top, which is also called as French top. The skin French top is constitutive of three layers. The hair is knotted tied on the middle layer, and then the hair is pulled out from the outer layer. It seems as if the hair is growing right from the scalp, and one can't see the knots from the outer layer, which is knotted/tied on the middle layer. The inner layer is a kind of net to make customers feel comfortable to wear.
A full lace wig is a hairpiece designed to cover the entire head and mimic natural growing hair. The hair is looped into a flesh-toned lace material, which, when glued onto the perimeter of the head, will create a natural-looking hairline and hair partings.