CMS full form is Content Management System. CMS is software that organizes articles or content of your websites. By using CMS you will easily create a lot of content.
Some popular CMS are:
1. WordPress (Free)
This is the most popular CMS in the world. The software is free and open source, many parties has developed the add-on software called Plugin. Right now you are see a WordPress website, Yes I am using WordPress too.
2. Drupal (Free)
Drupal is also popular CMS that we can use for free.