A cash drawer provides a means of temporarily storing cash during and between POS transactions. The cash drawer plugs into your receipt printer and waits for the printer to tell it to open. The printer waits for your POS application to tell it to print a receipt and open the drawer.
Pictures show the drawer with a 4 note setup vs a 5 note setup. For Euro it is advised to go for a 4 note setup since notes are quite wide. When split for 5 notes the slots are 6.9cm wide. When split for 4 notes they are 8.5 cm wide.
The drawer has a slot in front so that cheques and other larger notes can be slotted under the coin tray.