The feature-request tag wiki explains the tag (emphasis mine):
You have an idea for a new feature to be added, or for a change in existing functionality. Great!
Your question should contain the details of your proposal, including a justification of why the new feature is needed and/or how it can improve the community. Basically, prove to the administration that they should spend time developing your feature.
I think that explains the tag nicely, basically you use it for things that can only be done by Stack Exchange (and not the community). There are four ways your request may go:
Worth noting that whether feature requests will be implemented or not is completely up to Stack Exchange, it's not uncommon for massively upvoted requests to be declined.
I am asking if Stack Exchange treats the feature-request differently from other tags, and if so how.
They gather around a round table, and discuss the feature for a while. Then Rebecca Chernoff decides if the feature will be build or not. Most of the times the rest of the team is under the illusion that they had some say in the final decision, but it's always rchern, the puppet master, that decides. (: