A "redirect" is a command that automatically redirects a web browser from one page to another.
For example, if someone goes to https://www.wikitree.com/wiki/Help they will automatically be redirected to https://www.wikitree.com/wiki/Category:WikiTree_Help
The redirect happens because we have manually placed the following command on the page "Help":
#REDIRECT [[:Category:WikiTree_Help]]
You won't ordinarily see this because if you go to Help you will automatically be redirected. :-) You can see it by going directly to the edit page, i.e.: https://www.wikitree.com/index.php?title=Help&action=edit or https://www.wikitree.com/index.php?title=Help&redirect=no
See https://www.mediawiki.org/wiki/Help:Redirects for more on redirects in wiki mark-up.
Redirected Profiles
Redirects are very important on WikiTree. Every time profiles are merged a redirect command is added to the merged-away profile so that anyone who visits it is automatically redirected to the merged-into profile.
For example, if Smyth-1 is merged into Smith-1, the following command will be put on Smyth-1:
#REDIRECT [[Smith-1]]
It is important for advanced WikiTreers to understand redirects because of the "Multiple Redirects Problem" that happens when merges go in different directions.
Redirected Project Pages
WikiTree Leaders also use redirects to connect tags and projects when they don't exactly match each other.
See Adding Redirects for Project Tag Alternates.
Almost every one-name study project needs a Leader to manually add a redirect because one-name studies almost never use Project: pages. They are usually done with free-space project pages.
In order for our system to recognize that there is a Smith project, for example, there needs to be a redirect command at Project:Smith that has the actual project page name. In this case, https://www.wikitree.com/index.php?title=Project:Smith&action=edit has this command on it:
#REDIRECT [[Space:Smith Name Study]]