Flat Cards are a flat card, printed on one side. These are usually placed on each plate, folded into a napkin, or put into a frame.
Flat Cards/Double Sided are the same as above, just printed on both sides. Commonly used for extremely lengthy menus, or you could include a thank you note or schedule of reception events on the reverse.
Tented menus have a fold at the top, will stand on their own, and are printed on both sides.
Booklet menus are folded in half into a booklet - usually with a cover design, an inside left, an inside right, and an optional back page.