A domain name is your website URL, http://www.top6webhost.com and can be analogised to a home address. Common Top Level Domains are .com, .net and .org.
Web Hosting (a server) is space rented out where your files are stored. You can install many framework apps through an Installer which can be found in cPanel. Your files are what visitors and customers will view once they've arrived at your Domain. Files are the same as any other file you normally use such as .txt or a .gif image. The server automatically interprets these files which explain how the webpage appears.