Web hosting is, more or less, an agreement between you and a web hosting service provider that you will pay a monthly lease to own and operate a portion of their massive web servers. These are computers that will house all of your data and will allow others to get a good look at the content you so painstakingly create. Think of it as a storage unit with windows that other Internet users will drive by and take a peep through.
In order to operate a website you absolutely need a web hosting account, as no site can just live on the Internet without a web server. Since a web server usually costs thousands of dollars it is much more affordable to simply lease one from a web hosting provider. Web hosting services give you the opportunity to reach the world wide web without making a significant investment.