The Project Brillo is an 'underlying operating system for the internet of things'. Brillo is 'derived from Android' and has been polished to the lower levels, which is basically the 'lower layers of Android'.
Brillo, supports Wi-Fi, Bluetooth Low Energy and other Android things for devices with minimal footprint. Google is also working to include support for low power wireless solutions with three teams including Nest, Android and Chrome.
Google Brillo is designed to connect and run on multiple low-powered devices, that connects anything from door lock to a washing machine and linking with the existing Google technologies.
The IoT basically describes an environment where everything is connected to the internet, by creating 'swarm intelligence'. Devices like Bins, toasters, light, washing machines, door locks and even roads will be able to communicate to each other for automatic, and more efficiently can be controlled and monitored.
Brillo based devices will use a common language called WEAVE and its communications layer by which the internet of things can talk to each other. It means, Brillo devices, Cloud and your Android smartphone can be on the same platform.
The developer preview of Brillo will be available in the third quarter of 2015, while WEAVE in Q4, 2015.