Brillo is an Android-based OS focused on security and optimized for resource-constrained IoT devices. It uses the Linux kernel and provides core services like a hardware abstraction layer, runtime, application framework, and native services. Brillo emphasizes security features like SELinux, verified boot, and encryption. It is built using the Yocto Project and can be customized and installed on devices with a minimum of 32MB RAM, 64MB storage, WiFi and Bluetooth connectivity. Creating a Brillo product involves obtaining hardware, installing a board support package, and adding application services.