First of all, Joomla is most frequently used Content Management System 
nowadays. Joomla is most used for developing web portals and web 
applications. One of the major advantages of joomla is that it is simple
 to understand and use. Also, Joomla provides the facility of 
multilingual in which means you can build a website in English, and 
create another version of the same site in other languages such as 
French or Spanish. In addition to that, Joomla allows you to set the 
meta description and meta keywords of any of the page which is benefited
 for the Search Engine Optimization. Moreover, If you need to create a 
custom form in Joomla, there is already a component for that. If you 
need to integrate social networking into your Joomla website, this is 
already done for you.
Secondly, Joomla is fast, safe and it is easier to locate content in 
Joomla than in other CMSs and to edit that content. Afterwards, Joomla 
is so popular in the CMS world and its easy menu creation tool. All CMS 
veterans can attest that Joomla has the easiest and most powerful menu 
creation tool.
Thirdly, Joomla is created using PHP and uses MYSQL for data storage. 
PHP is the most important open source web scripting language at the 
moment and MYSQL is the most powerful and most used open source 
database. So, Joomla is the 100% open source platform. There are many 
Joomla development companies which you can take a solution for the 
joomla development.
Forthly, You download it for free, you use it for free and you upgrade 
it for free. You only need to pay for your Joomla website. To know more 
about the Joomla, you can check 
http://www.joomla.com.