Before Wordpress there was a blogging tool called b2/cafelog, otherwise known as b2, which Wordpress was made as a fork of. Wordpress version 0.7 was released in May 2003. Even since then, new versions have progressively added new features: including plugins, themes/templates, security and SEO.
Wordpress.org is where the Wordpress software can be downloaded for free for anybody to begin making a website. However you will have to take care of the hosting yourself.
Wordpress.com is a for-profit company that provides their own hosting services that anybody can pay for. The less tech-savvy you are, the more likely it is that you will want Wordpress.com to take care of the hosting and site management for you.
Wordpress is by far the most popular CMS in the world, mainly due to the open-source ecosystem that incentivizes developers to continually improve and expand upon its functionality. There are both free and paid versions of Wordpress, and it is up to the user to decide which option is best for them.