When a link in Wikipedia leads to nowhere, it is displayed in red to alert our editors that it requires attention. A red link can mean one of two things:
The link is broken and no longer leads to an article (perhaps because the underlying article was deleted). In such a case, the link needs to be removed or renamed to point to an existing article.
A new article is needed. When a Wikipedian writes an article, it is common practice to linkify key topics pertinent to an understanding of the subject, even if those topics don't have an article on Wikipedia yet. This has two applications:
From within an article, such a link prepares the article to be fully supported. At any time, a Wikipedian may independently write an article on the linked-to subject, and when this happens, there's already a link ready and waiting for it. The red link also gives readers the opportunity to click on it to create the needed article on the spot.
In topic lists, it is useful to include every topic on the subject you can possibly find or think of. When they are turned into links, the list immediately shows where the gaps in Wikipedia's coverage for that subject are, since all of the topics missing articles will show up in red. Such lists are useful tools in developing subject areas on Wikipedia, as they show where work is needed most.
This user prefers using userboxes to fill up their user page instead of actually writing something useful.
This user is aware of how silly this huge table looks on their user page, but acknowledges that its real purpose is twofold: statistics and standardization.
-xen
This user believes that userbox should always be pluralised userboxen, and thinks that this is one of the most important and exciting issues of our time.
This user will move to a GSV at the first opportunity.
their there they're
This user thinks that there are too many people who don’t know that they're worse than their own children at spelling!
your you're
This user thinks that if your grammar is incorrect, then you're in need of help.
its & it's
This user thinks ohh, if you want it to be possessive, it's just i-t-s, but if it's supposed to be a contraction, then it's i-t-apostrophe-s... Scalawag.