(Definition adapted from TechTarget.com)
WEBSITE = A Web site is a related collection of World Wide Web (WWW) files that includes a beginning file called a home page. A company or an individual tells you how to get to their Web site by giving you the address of their home page. From the home page, you can get to all the other pages on their site.
P.S. (from: TechTerms.com)
"Please note that a Web page is not the same thing as a Web site. A Web site is a collection of pages. A Web page is an individual HTML document. This is a good distinction to know, as most techies have little tolerance for people who mix up the two terms."