The term 'thin cookie' can refer to two different types of cookies: wafers and snaps. Wafers are thin, crisp cookies made from flour, sugar, and other ingredients. They are usually round or rectangular in shape and can be plain or flavored. Snaps are also thin, crisp cookies made from flour, sugar, and other ingredients. They are usually round or square in shape and have a SNAP when broken. Both types of cookies are popular treats and can be enjoyed with a cup of tea or coffee.