Shirt is an upper body garment which has collar and cuffs having a front button down opening. Shirts are basic essentials all need to have in variety to choose. Shirts can be multipurpose and can be paired with trousers, skirts, or blazers, creating a wide variety of distinct fashion ensembles.
Boxy as the name suggests means "like a box". Boxy fit is meant to just hang off of a person's body loosely. The garment when laid flat looks squarish and hence the term boxy fit.