Not as vague as you might think. This is a very commonly used approach. What I would suggest you focus on is creating a custom post type. This will give you the admin menu item, categories (or any taxonomy structure you like) and many other features.
CPTs are very simple to register and modify. They are perfectly suited for storing data such as products in a store, destinations for a travel site, etc.
Full documentation for the register function ( register_post_type() ) can be found here