Domain names are not free, however, many hosting packages include a domain name with a year of hosting services. You can buy your own domain and host anywhere, it does not need to be all from one place. The annual domain renewal fees need to be paid once a year to the registrar of your domain no matter where it is hosted. That is usually from $10 to $20 but there are cost differences, even between .com and .info for example. Hosting (basic, shared-server hosting) can be found for under $5 a month and often includes a site builder tool. Specific recommendations would be against the Charter of this forum: [
webmasterworld.com...] you'll need to look around and compare what is out there.
You can change your domain registrar almost any time you like, some restrictions apply to transferred or renewed domains, some registrars make it easier than others, it is usually free to change registrars.
Using a sitebuilder will often restrict you to being unable to change to a different host. You might want to change to a different host if you are unhappy with the service they provide or want features they don't offer, or find a better host or - lots of reasons. Hosting your domain is not free, though there are sites that will give you some free space that they use to show advertisements with your content.
Self hosting is hosting done with your own equipment, but you would need to be prepared to do your own setup, configuration and maintenance, not a good place to try to start out.
CMS is "Content Management System" such as Blogger (free) or Worpdress (free for non commercial sites) and it is a good place to start your learning. Wordpress can be exported to your own domain and hosting after you learn all the ins and out of managing your site. There are lots of tutorial type sites to help you no matter which way you decide to start.
The one thing I would add which you did not ask about is that you should begin learning html and css so that you can know how to make your site the way you want it to be, even if you use a CMS - it doesn't need to be a cookie-cutter copy of what everyone else has.
I hope you like to read because before you get far you will need to read, read, read to learn and then read, read, read to keep up.