a link connects pages and everything else
Since you're reading this, you already know what a web link is. In wikis, links can connect to pages, news, attachments, spaces, other web sites, and pretty much anything accessible using your browser.
The trick is to design your wiki so that common navigation links are available on all pages, so they don't have to be manually added to every page. You can accomplish this either by modifying the layouts or with a [custom theme].
Example
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Aliquam fermentum vestibulum est. Sed quis tortor.