EDIT: This is a nice ready-made menubar application here (github source) by this answer.
I was wondering how to make a menubar application, what are the requirements for that to do so?
I saw a simple application for the menubar was to open links using your browser, I want to create something similar to that.
This is the application I like to make similar.
NSStatusItem is what you are looking for. Also add LSUIElement with string value of 1 to your Info.plist to hide it from Dock.