For this game, information like this is in popular discord servers like The Balance which link odd google docs, but there have been attempts to put some of it onto websites.

There isn't just one website like wowhead and instead there are lots of websites with very specific uses, but saltedxiv is the closest attempt to make something resembling it that I know of.

Information like item and quest databases and user interface guides is available on Square Enix own website called the Lodestone.

You can usually find these discord servers linked in the reddit posts that come up on google.