Arduino shields are plug-on expansion boards that stack directly onto an Arduino Uno or Mega, adding new capabilities without requiring custom circuitry. They follow a standardised pin layout, making them interchangeable and easy to combine.
Available shields include motor driver shields for controlling DC and stepper motors, relay shields for switching mains-voltage loads, data logging shields with SD card and RTC support, Ethernet and WiFi shields for network connectivity, and prototype shields for custom circuit work.
Shields are widely used in education to teach specific electronics concepts with minimal wiring, and in prototyping to rapidly validate ideas before committing to a custom PCB. Common applications include home automation relay control, GPS data logging, motor-driven robots, and remote sensor networks.