How do I get a wiki link to redirect to category?

Lets say I have a category 'People'
And I want to make sure that all mentions of the word 'People' will redirect to this category. How do I do this?

If the category's name is exactly "People" with no prefix, then a link to "People" should resolve to the category, no redirect required.

Shouldn't all categories have the category prefix?
If not then what's the purpose of this prefix?

Prefixes are arbitrary. The category may or may not have the prefix "Category" as part of its title. In VaultWiki 4, the behavior / "treat this page as" is not tied to a specific prefix like in VaultWiki 3. In VaultWiki 4, there is more flexibility. In VaultWiki 4, prefixes are for naming purposes only.

VaultWiki 4 only comes with one prefix, the Special prefix, which you can rename, or not use at all (you can rename Special pages nowadays).

Most categories that were imported from VaultWiki 3 would have been imported with a prefix though. That prefix is most likely whatever the name of your Category namespace was in VaultWiki 3 (still arbitrary, since the VaultWiki 3 installer did not create this namespace automatically). But again, this imported prefix only has a naming purpose now. It is not what makes a "Category:" a category.

Thanks for explaining. This is very helpful.
In VW3 we had it set up like this:
Category:People - to make the page a category.
In our Redirects area: People (page with redirect to Category:People) - To make autolinks work.

Now after VW3 to VW4 import the redirects have not become synonyms of the category pages. The wiki redirects forum has about 70 redirects to categories. For some reason the redirect code is gone from these.

It seems to me that the best approach is to:
1. Delete these 70 redirects from the redirects area.
2. Then remove the Category prefix from 219 pages.

Am I approaching this correctly?
is there anything I need to be mindful of?
is there a way to do this quickly?

I have reviewed your Wiki Redirects area and it looks like redirects that used the REDIRECT code were imported as synonyms as expected.

However, the following entries were not imported as synonyms:
- NuWiki-syntax redirects if the source legacy-code mode was not set to NuWiki
- MediaWiki-syntax redirects if the source legacy-code mode was not set to MediaWiki
- entries in that area that did not use the REDIRECT code, but which used only the CATEGORY code (presumably as a link) were imported as regular pages. The CATEGORY code was correctly imported by placing the page into the specified category.

In general, it looks like that Wiki Redirects part of your site needed maintenance. Your approach of deleting the 70 redirects, then removing the Category prefix from pages is a solution that could work. However, at this time, there is no mass-rename function (but it has been requested already). The current fastest way, modifying the vw_revision table and setting prefixid = 0 where prefixid = CATEGORY_PREFIX_ID, would not give you 301s to the unprefixed categories (although you can easily do this via .htaccess), and it may result in additional URL Conflicts. If you go that route, you will need to rebuild your URLs in the Maintenance > Rebuild Counters page, and you will need to manage your duplicates on the URL Conflicts page.

You might do well to visit the URL Conflicts page before you do any of this, and manage the entries that are already listed (make sure to check each prefix). After doing this, you will be able to check each page in Wiki Redirects with confidence, because it's possible they are not all old redirects.

Thanks for looking into it. That clarified a lot.
I have now removed all redirect pages and the redirect area. I also removed the wiki pages area because it seems cleaner that way.
Is it possible to remove the 'category' prefix manually from a page?

Yes, assuming the area allows a choice of various prefixes, when editing the page, there will be a prefix drop-down next to the title.