For all Joomla 3+ templates built using the Zen Grid Framework v4 (any theme after October 2014) please refer to the Zen Grid Framework v4 documentation.
The performance tab in the template parameters offers a selection of improvements to the speed and optimization your website.
Compress system and core CSS files: this option enables the compression of all CSS files that are loaded by default into your site. Please note that this is not include the CSS loaded within the child theme or the other CSS files that might be loaded by other joomla extensions.
Remove Joomla meta-tag generator: By default Joomla adds its own meta-tag to the output of your website. While this setting tends to have no direct effect on your website performance it may be of help from a security perspective to remove this meta-tag to reduce the ability for hackers to identify your site as a site that uses the Joomla CMS.