Any situation wearing clothes from outdoor to going out clothes to uniforms. The clothes can be of any type for any purpose but worn in a way that would be considered normal wear. Often this is the category a model would start off doing, especially if they do not have a large wardrobe. It can be fun and gives an opportunity to get used to being in front of a camera and learn how to pose, usually this will be under direction from the photographer, gradually allowing the model to pose as they wish as they get accustomed to it.
Fashion would be the next category to go to logically but this need not be the case, having gained experience a model could then move to any other category they feel comfortable with.