HTML links allow users to navigate between web pages using hyperlinks. A hyperlink is defined using the <a> tag and contains an href attribute that specifies the URL of the destination page. By default, unvisited links appear as underlined and blue, visited links as underlined and purple, and active links as underlined and red. Images and email addresses can also be used as links. The <hr> tag inserts a horizontal rule and can be customized with attributes like size, width, and color.