As their names suggest, skinny and slim are two types of jeans. Both models are made of denim and will hug the person's body. Skinny jeans fit tightly around one's legs and hips. Slim jeans are also tight, but they will contour to the shape of the person.
Skinny jeans are tighter, and because of their tight fit, they are less comfortable than slim jeans. Despite their lack of comfort, skinny jeans have a better appearance to them. They provide a cleaner and sophisticated look than slim fit jeans do. Skinny jeans are great for those that wear heels and flats, while slim jeans look better for those that.