Bookmarks are useful on long pages.
A web page designer can create a list of hyperlinks at the top of the page and each hyperlink can link to a bookmark on the same page. You can change the bookmark name, but most of the time you probably will not. The bookmark will be denoted by underlining the text with a dashed line. It is also possible to create a bookmark at a cursor position without selecting any text. If you do this, you will have to provide your own bookmark name, and the bookmark location will be denoted by a blue flag.