I recently gained the ability to approve tag wiki posts, but I am not sure what these are or where to access them.
A tag wiki is a short blurb describing/defining that particular tag, to guide users in deciding when that tag is appropriate to use on their question.
I found this blog helpful in explaining what and why tags exist.
If you have expertise in a particular tag area, and if you have sufficient reputation points (10 points) you can suggest edits to the tag wiki, and are encouraged to do so if you see a tag wiki is lacking the relevant information.
To do so, click on the "Tags" tab on the left, select a tag (such as "localization") and on the tag page, at the top, it will say the "usage guidance" and if it doesn't exist, click the "help us create it" link to provide a suggested definition.