Answer -
Wordpress is the best open source CMS which allows it to be free of cost that is it can be used without any charges totally free.
Anyone can use it for either personal branding or by the organisation too.
It is a blogging platform .
No single penny is required to use it .
It is build on php /mysql (which is an open source and also licensed under GPL .)
**CMS IS A CONTENT MANAGEMENT SYSTEM that is used to edit ,create ,modify and publish
digital content .It provides a common user interface which subsequently allows multiple users to publish updates live on the web .***
***GPL is General public license most widely used free software license
Originally written by richard stallman for the GNU Project .***