Basically, WordPress is the backend (dashboard) of your website.
All the pages, blog posts, menus – all the content really, is managed here.
Everything that you create is in your copyright.
This includes the design that was made for you.
The only thing that isn’t “yours” is the engine that runs the show. This is WordPress.
WordPress is Open Source, which means it isn’t really “owned” by anyone.
It is available for free download, and unlimited usage, and can be hosted with any capable hosting company.
There is no need to own it, for it is freely available to everyone.
Conversely, websites developed on Proprietary platforms have none of the above benefits.
You may have copyright ownership of the content you create, but it ends there.
The website, the design, the engine, all of it is owned by the company that you are “renting” it from.
Should anything happen to your relationship with a proprietary website company, you are likely to lose everything.