Jaws can be mismatched in a number of ways:
When the lower jaw is too short relative to the upper jaw it will appear that the upper front teeth are sticking out too far. The profile will show a weak or retrusive chin and a convex profile. This is by far the most common mismatch of jaw growth.
When the upper jaw is too short relative to the lower jaw it will appear that the lower teeth are sticking out too far and the profile will show a strong or protrusive chin with a straight profile. This is a relatively rare mismatch of jaw growth. This often results in an underbite or anterior crossbite, where the lower front teeth are ahead of the upper front teeth instead of the other way around.
When the upper jaw is too narrow relative to the lower jaw the side teeth can go into crossbite with the lower teeth on one side or sometimes both sides. The upper side teeth are normally further out towards the cheeks than the lower side teeth. When these side teeth are in crossbite the lower side teeth are further out towards the cheeks than the upper side teeth.