The interwebs are full of comparisons of WordPress dot org and pretty much everything else, including its sibling WordPress dot com. Basically WP dot org is free, open-source CMS software that I self-host using my own domain name and a commercial hosting provider of my choice. It has a bit of a learning curve but limitless possibilities. WP dot com is a commercial entity that offers to host my blog on its servers. It is easy to use and offers a free tier but is somewhat limited – especially on the free tier. It is frequently compared to Google Blogger.
Really no need for me to add more – except for my point of view.