LittleBits are modular electronic building blocks that are color coded into four categories: Power, Input, Output, and Wires. Power modules must always come first and provide energy to the circuit. Input modules accept signals and pass them to following Output modules, which perform actions like lighting or moving. Wires allow physical separation of modules. The document provides examples of modules like lights, motors, and sensors and instructs designers to use the provided materials to build their own project within 20 minutes in teams of two.