Cache can be best defined as the process of storing frequently used data, usually data that is costly to generate, for reuse, typically this data is stored in memory since retrieving data from memory is much more efficient than retrieving the data from other locations, such as a database. Joomla has its default caching facilities.Moreover many free caching components and modules are available for download.
Basic advantage of Caching.
It increases the page loading speed of your website or web Blog.
It drastically reduces load on the server.
It accelerated the overall performance of our Joomla website.
A standard Joomla website generates all the pages dynamically from SQL database which make the page loading time reasonable slow. Specially when your website get traffic above average ,it become even every slow. So to increase the performance of our Joomla website we definitely need to enable cache in Joomla.