With the help of a shaving brush, shaving soap or cream is foamed into a rich shaving foam that protects the skin during shaving and improves the glide of the razor. In addition, the suti lifts the beard hairs from the skin and the foam gets where it is needed, on the skin. The differences between Suti arise in the material choices for the handles, as well as what type of hair is used in Suti. More specifically about shaving brushes from here from the article.

Horse wolves - Compared to wild boar hair, horse hair wool is softer and the hair is obtained from the care of the horse, in connection with brushing.
Badger wolves - Really soft and perfect for facial foaming. The bundle contains a large amount of fine hair.
Mixed smokes - Contains two different bristles, one providing softness to the face and the other a backbone for foaming.
Synthetic - Made of plastic fiber. They do not require pre-soaking and dry quickly after use. A truly worry-free option.
Wild boars - Well suited for foaming hard soaps. They require several uses, when the bristles naturally divide and become softer on the face.