Random Fonts assigns random web fonts to elements of your site. Use it if you want to spice up your site with some web fonts, but just cannot make a choice. Just so we are clear - this module is supposed to be used in the development stage, not on production sites.
Shipped with this module is another one, Ransom Note, which lets you create mixed font displays looking like just that.
These modules do not depend on each other and even aren't meant to be used at the same time. They're shipped together because they're both small and do weird things. :)
Both modules require @font-your-face.
Random Fonts also requires at least one of the following font provider modules to be enabled: Google Fonts API, Edge Fonts, or both. (These providers allow fonts to be used without complicated installation procedures.) For more information, see README.txt supplied with the module.
Ransom Note can work with any fonts from any provider. See its README.txt.