FTP, or File Transfer Protocol, is the method used to upload the documents, stylesheets and media contents to a web server to be hosted online.
It is necessary for putting the local files that we have been working with on the Internet to accessed by other people.
I use Cyberduck, which a free FTP client. It looks like Finder or a file browser, but it represents the file structure of the server.
Dreamweaver and other editors have FTP built in, which is a nice convenience. Fetch is another good FTP client, which can be used for free, asks for a donation. There are lots of FTP clients for pay or not.
Registering a domain and buying server space can be done on a number of websites. I use Fatcow. Dreamhost is also good. Again, there are lots of hosting services that offer different advantages and pricing. We'll look at the steps of registering a domain name and server space.