This lesson introduces matrix keypads and how to interface them with an Arduino board. Unlike single push buttons that require an individual pin for every switch, a matrix keypad uses multiplexing to arrange keys in a grid, allowing you to read multiple inputs using significantly fewer pins.

Topics covered: Introduction to matrix keypads, matrix multiplexing principles, keypress detection mechanisms, wiring keypad circuits to GPIO pins, utilizing the `Keypad.h` library, and programming exercises for serial monitoring, keypad pianos, and keypad-controlled servo positions.