Let us talk about what a website is first.  A website (alternatively, web site or Web site,) is a collection of Web pages, images, videos or other digital assets that are hosted on one or more web servers and usually accessible via the Internet. 

A web page is a document, usually written in (X) HTML that is almost always accessible by HTTP, a protocol that transfers information from the web server to display in the user’s web browser.

All publicly accessible websites will be seen collectively as constituting the World Wide Web. 

The pages of all websites can generally be accessed from a common root URL called the homepage, and will usually reside on the same physical server. The URLs of the pages will organize them into a hierarchy, but the hyperlinks between them control how the reader perceives the overall structure and how the traffic flows between the different parts of the websites.

Some websites will require a subscription to access some or all of their content. Examples of subscription sites can include many business sites, parts of many news sites, academic journal sites, gaming sites, message boards, Web based e-mail, services, social networking websites, and sites providing real time stock market data. This is because they will require authentication to view the content they are technically called an Intranet site. 

Ok, so what is a copywriter?  A copywriter uses words to help promote a persons business, opinion, or idea. A copywriter can also use plain text, as a radio or television advertisement, or in a variety of other types of media. The main purpose of copywriting, (also know as promotional text), is to simply persuade a listener or reader to act: to buy a certain product or subscribe to a certain viewpoint. Alternatively, copywriting can also be intended to dissuade a reader or listener from a certain belief or action. Copywriting in literal terms is getting across the perfect message, by using the perfect words.

Let us put the two together now.  A Web copywriter is simply one that writes copy for the purpose of using the internet as there forum.