Before applying any paint coating on any surface, you first need to know what type of paint is on the object or surface now. This is important because oil based paint and water based paint are not compatible. If oil based paint is on the surface now, you can go back with an oil based coating. Same thing if it's a water based coating, you can go back with another water based coating. But you cannot paint over a oil based surface with latex. It will peel. However some times you may be able to paint an Oil based coating over a Water based coating. Read the label first tho, as this is not a hard and fast rule. All you have to do, to change from one coating base to the other, is to rough up the surface by sanding and apply the right kind of primer. This seals the original surface and prepares it for the new top coat, oil or water based.
Traditionally in the past oil has been used on the exterior and the interior trim. Sometimes it was used in the kitchens, and bath rooms where a harder paint or a shine was desired. And of course on all metal objects. Today, Latex or Water based finishes are far more common in all these areas except for certain metals.
As a Pro I have looked at thousands and thousands of surfaces and items and can often tell what type of paint it is by experience. How ever sometimes even a pro needs to do a test. As always it's better to be safe than sorry. If you are guessing, then you should do the test.
The Test! - Place a small amount of Denatured alcohol, or paint Deglosser on a cotton Ball. Then rub the surface area with the cotton ball. If the surface is Latex paint, then the surface will become disrupted, the paint will be removed or the surface will become tacky. If the paint is Oil based nothing will happen to the surface.