Joomla! CMS has evolved over time with new improved versions being released time and again. Here's an overview of the advancement of Joomla! over time:
https://docs.joomla.org/Category:Version_History
To check what version of Joomla! your website is currently running on through the backend, follow the following steps here:
https://docs.joomla.org/How_to_check_the_Joomla_version%3F
Normally, you should use the latest version of Joomla! In order to update your Joomla! CMS to the most current version there is, go to:
If you're currently operating on Joomla version 1.5, you first need to migrate to Joomla! version 2.5 by following the steps here:
https://docs.joomla.org/Joomla_1.5_to_3.x_Step_by_Step_Migration
If you're currently operating on Joomla! version 2.5, you need to migrate to Joomla! version 3.x by following the steps here:
https://docs.joomla.org/Joomla_2.5_to_3.x_Step_by_Step_Migration
