Building ChromiumOS from source can allow you to breathe new life into Chromebooks that have reached its End of Life Date (EOL) by allowing you to apply the latest security patches and some new security features that are often reserved for newer models of ChromeOS devices. In addition to being able to create a build of ChromiumOS that can be used on first party hardware that shipped with ChromeOS out of the box, you can also create builds/ports for hardware that was designed for other operating systems such as generic desktop/laptop computers and single board computers.
This section of the guide does deal with several advanced concepts however it is written in a way that allows a user to copy/paste most of the commands into a terminal to perform the build.