WP Rig’s file structure is different from the typical WordPress theme, but has recognizable pieces, like styles.css, sidebar, screenshot, header, footer, functions and so on. There are also new pieces. That is because WP Rig is not a starter theme — it is a theme development rig, meaning it is an entire toolkit used to build a theme. In short, WP Rig is a re- imagining of how WordPress themes work, and how they should be developed.
When you’re done and your theme is ready to be published to a custom site (or the WordPress theme directory or a marketplace of your choosing) you’ll run an export process to generate a new folder with just the necessary theme files. That means you can generate as many different themes as you want from one single WP Rig instance.
But, it is recommended to set up separate environments for each theme you build. The beauty of WP Rig is, you don’t have to know what’s going on in the build process, unless you really want to. The build process is built to be updated, and configurable and easy to understand. (You can find it in the Gulp folder if you want to take a look.)