If we were preparing a technical HTML document, this page might contain additional explanation that would be useful to some viewers of the document and unnecessary for others. Tucking away supplementary information in a separate place can help keep the main document uncluttered.
Clicking on the link (the shortened name usually used to refer to hyperlinks in practice) below takes you back to exactly the point in the previous document from which you jumped to this page. You can achieve the same result by clicking on the back button on your browser.