Ready Made Sites are pre made site combinations with images and content to replace that you can install from your WordPress admin section to have a site working in literally minutes. A collection of sites created to fulfill a specific purpose: an agency site, a blog, a shop, etc.
A RMS is a pre-built configuration + content of the theme that you can install and then modify as you want.
Each theme comes with its own RMS ready to install, and they’re all included with your theme’s purchase license.
Take a look at them here.
Images on the Ready Made Sites preview are for demonstration purposes only. When you install the RMS you’ll see placeholder images which you can later on replace for your own images.