The Raspberry Pi is a small, low-cost computer that can connect to a keyboard, mouse and monitor. It runs Linux and allows users to explore programming through languages like Scratch and Python. The Raspberry Pi has GPIO pins that enable controlling electronic components for physical computing projects. It comes in different models that vary in processing power, memory and connectivity options. Python's RPi.GPIO module allows controlling the GPIO pins to take sensor input and drive outputs. Code examples demonstrate setting pin modes, reading/writing pin values and using an IR sensor for obstacle avoidance.