Triptych Card

"A triptych ( /ˈtrɪptɪk/ trip-tik; (from the Greek adjective τρίπτυχοs ("three-fold"), from tri-= "three" + ptysso= "to fold") is a work of art (usually a panel painting) which is divided into three sections, or three carved panels which are hinged together and can be folded shut or displayed open. It is therefore a type of polyptych, the term for all multi-panel works. The middle panel is typically the largest and it is flanked by two smaller related works, although there are triptychs of equal-sized panels. The form can also be used for pendant jewelry."
This definition is from Wikipedia and it also applies to cardmaking.
If you type Triptych Cards into google images you will find all sorts of shapes and sizes. They are fun to make.