Smartthings is a home automation solution that connects regular devices to the internet through a central hub device. The Smartthings hub allows users to monitor and control connected devices like sensors and appliances from their phone through apps. It supports various technologies like Zigbee, Z-Wave, and IP to connect devices for basic functions like security, presence detection and environmental monitoring. Popular Smartthings devices include motion sensors, door/window sensors, sirens and temperature/moisture sensors that can automate home security and convenience through the Smartthings platform.