Links are how visitors get from one page to another. You'll probably put a lot of links in menus – a menu being just a list of links to other content. But you may also place links directly inside content text, or inside a block's text.

You may want links that point to a specific content item on your site, or a specific page on an outside web sites. Or you may want powerful links that pick up and return a list of multiple content items from your site's database.

This is important stuff. One of the keys to grasping Drupal is to understand that creating content is just a small part of the picture. Creating a node is simple enough; telling users how to get to any node, via links in menus or elsewhere, is the start of building a site.