The main difference between fry pans and French skillets lies in their sides. Fry pans have low-sloping sides, allowing you to flip and toss food items but limiting their capacity for holding more liquid or food.
Stainless steel is a versatile material and holds heat well. Many stainless steel skillets are safe to place in the oven (make sure there aren't any plastic parts, though), which is handy when a recipe calls for searing fish or meat and then placing it in the oven to finish cooking. This saves time because you don't have to transfer the ingredients to another dish to bake or roast in the oven. This is, of course, also useful in terms of clean-up being that you don't have to dirty up another receptacle.