First thing you should know is, there are two different versions of WordPress:
WordPress.org
This is the 100% free opensource platform that anyone can download and install on their own domain and hosting. This is the most flexible and you have complete control over the management of the software. You can use it to create custom blogs, websites, and whatever you can dream up.
WordPress.com
WordPress.com is a hosted version that is also free with paid versions that let you add your own domain. This great for first-time bloggers or people who don’t need fancy plugins or customizations.
There are pros and cons to both platforms but for the sake of our tutorials, we are focusing only on WordPress.org which is what our theme was created for. For more details and comparison of the two platforms, you can take a look at this post from wpeginner.