There are many types and applications of badges/buttons.
The pin back can be metal or plastic. For metal pinback, there are two kinds of pins and for plastic pinback, there are also two kinds of pins.
And the metal surface can be frosted or shiny. Also we have magnetic badges/buttons with flat back:
Besides, we have mirror buttons, magnetic bottle openers, these products with keychains, and photo frames, rosettes to be made.
Examples partially as below:
Note: All things introduced above are of the basical round shape, and we also have other shapes of badges,buttons. Furtherly other types too.