Look at personal physique. It depends on whether this shirt is short or long. If it's a short shirt, you don't have to stick it in the skirt. If it is a long shirt, it needs to be inserted into the skirt. Putting a shirt into a skirt will make you slimmer. Shirts can be divided into pointed collar, square collar (corner collar), round neck (pill collar) and cardigan, and other collar types are called special collar types.