Joomla is an open source content management system (CMS) designed to enable you to create a website or blog from scratch, or to improve an existing website. Joomla was first released in 2004, and it is currently the most popular content management system in the world. Joomla is available in two versions – Joomla! and Joomla! 3.x.
However, Joomla has also been known to be vulnerable to security threats. As such, it is important to keep your Joomla installation up-to-date with the latest security patches. Additionally, you should only download Joomla from official sources to ensure that you are getting a safe and secure version of the CMS.
Joomla! is the original version, and Joomla! 3.x is the latest version.