A dangling link is a link that is formed when you write a new WikiWord onto an existing page.
HereIsADanglingLinkExample? (but please don't click on this question mark, or it defeats the purpose of the example)
The DanglingLink has a question mark after it. This allows one to click it and edit that WikiWord as a new page in the wiki. This makes the DanglingLink disappear, replaced with a normal WikiWord link to a page. But again, the DanglingLink above is for demonstration, don't click it please.
See WantedPages for a list of all dangling links on the Wiki. Please note that not all those dangling links deserve to have a new page created for them. If you're looking to contribute to the Wiki, the WhatIsaWiki and WikiToDo pages might be a better place to start from.