To improve the performance of a Joomla! site it is recommended to enable cache.

This can be done easily from "Global Configuration":

1. In the backend Joomla! administrator panel head to Site -> Global Configuration -> System
2. In the right panel you will see the "Cache Settings" tab: select "Yes" for cache and save the changes.
3. The "Cache Time" can be changed according to your website needs.
   If the site content updates often it is better to set a lower cache time (news website, sites with a shopping cart)