Services is a general name for things your inn offers, other than food and drinks.
In the Services Window you can see the list of your rooms, along with their cost and quality. You can press the magnifying glass icon to see more details (Room info) or the eye icon to see where the given room is. In case of Private rooms and Guest rooms you can also set their rent and see how well your guests will react to it.
The Room info window shows you the quality of the room and what affects it: appearance, size, and cleanness. The window also shows what style they given room is representing.
In this window you can also change the type of the room (for example change a Storage to a Bathroom and so on), changing its properties, as well as rename it, to make finding it on the list easier.
Below that you can see the list of services offered in that room (eating, gambling, and so on) and, in case of Private rooms, whether and by whom it's rented (you can also get rid of the tenant).