A domain name is what people will search in a browser to find a specific website. To purchase a domain name you must first think of a name which would best describe your website. Usually website names are fairly short or catchy so the audience remember it.
Web hosting is used to publish websites on the Internet. If you make a website and want people to be able to view it then you must upload it on a web hosting service so people search for your website and then view it. You can use many things from web hosting; From personal designed websites just for fun to online shopping websites. Without a web hosting service people will not be able to view your site.
When your website is going live onto the world wide web, a live search team will be needed to make sure your website will come high in the listings when key words are typed into specifc search engines, this will make your website more visible therefore, hopefully more people will view it.