An I2C 16x2 LCD Display is a popular alphanumeric module (16 characters, 2 rows) for Arduino/microcontrollers, using an I2C adapter (PCF8574 chip) to drastically reduce wiring to just four pins (VCC, GND, SDA, SCL), allowing you to display text with an adjustable blue/green backlight, saving valuable microcontroller pins for other uses in DIY electronics and robotics projects.