The command tells the page what words or images to link, and what page to load if the link is selected. As with many HTML commands, it has a beginning and an end. This is safe to be sure you always get to a particular page, even if you just copied the link from somewhere else. If the desired page is in a different directory, such as my main home page, you can also state the directory structure. This allows you to reference pages within your own directory easily, even if you change the host of the web pages.
External links go to some other page, and use the notation shown above.
Internal links provide navigation within a page, such as the index links at the top of this page. This identifies a specific location on the page to which anyone could link directly. This allows the user to send email to the specified account automatically with the click. The information between the quotes is your email address. Use these links a lot to help explain your page, or to provide more information about topics you have selected.