A company or organization usually only has one web site. That web site consists of hundreds, or even thousands of web pages. A web page is, well, like one page in that book. You may have one page selling this product, or another page explaining this idea. More importantly, you need to understand that each web page is a computer file.
Home pages are web pages.
However, they are special web pages. Think of the home page as the table of contents in that book. It's where you want the visiting public to go first. From there, they can go to any other page on the site. All web sites only have ONE home page.