OpenWrt is an open source project for embedded operating system based on Linux, primarily used on embedded devices to route network traffic. All components have been optimized to be small enough to fit into the limited storage and memory available in home routers.
Another feature of OpenWRT is the unified configuration interface UCI (Unified Configuration Interface), which allows you to manage most system settings using a single syntax of configuration files and command line.
The UCI configuration files are located in the /etc/config branch, and can be edited by a human. To view and change the configuration settings, use the uci utility too.
There is also a standard LuCI web interface (Lua Configuration Interface), which uses the UCI to retrieve system information and make changes to its configuration.