A link is a way to link your article to an external source. It could be a link to your company homepage or any other documentation that might be relevant.
You should give your link a name that is descriptive and you'll be able to find it easily to add into an article adding in a description on what the link is.
Editing and Deleting a Link
It is advisable to check these links regularly to ensure they work and the page is up to date.