This feature creates the cache for mobile devices. This is a premium feature. It does not exist in the free version.
Responsive Theme without Lazy Load Option
If you use a responsive theme, no need to use the mobile cache feature. You should disable “Mobile” and “Mobile Theme” options.
Responsive Theme with Lazy Load Option
If you enabled the Lazy Load option, you need to enable both “Mobile” and “Mobile Theme” options because Lazy Load works differently for the mobile devices.
If you use a mobile theme, you should enable both “Mobile” and “Mobile Theme” options.
How it works
The feature creates a folder which is “wpfc-mobile-cache”.