This module has 16 push buttons. You can make usual keypads to enter numbers, symbols, or do navigation and selection in the program. There are pull-up resistors of different values for each button. This makes it possible to connect all the 16 keys and taking only one analog port of the microcontroller. Each button consists of two parts: a cap, which can be applied to any character, and a transparent cover which can prevent blurring of the text and add light.
After connecting power to the module and pressing at least one key, the "OUT" pin will provide the appropriate voltage level. A table list is provided at the back of the board to show the different pull-up resistor values for each key (values are valid when powered from 5v).