They get you from one site to another and between pages within a site.
Most people recognize links as images or text in a different color that are underlined.
You know if something is a link because the cursor changes from an arrow to a hand if you move your mouse over it. Below is the code for a common, basic link. The resulting output will be Click here to visit Yahoo. The code that goes in the quotation marks after it is the page that you want to send the visitor to. All you have to write is the information within that folder.