Defaults to the caching level option you have in your Cloudflare performance settings for the domain.
Will not cache at all
Standard / Aggressive caching
Caches all static content that has a query string in it
Ignore query string
Caches static content that has a query string and treats it as one file
Caches all file types on your site, including static content and HTML. Cloudflare Cache Everything will automatically respect any default cache headers set by the web server or CMS software like WordPress. See this article for more details on how headers affect this setting.
**NOTE: When using "Cache everything" you might have trouble with login forms on your site. A common one is WordPress. To correct this you'll need to add another rule as the first rule for the wp-login.php file that is set to "bypass cache"**