The difference with the premium fuels you see at many petrol stations is that they contains more octane. Octane is an ingredient in petrol that allows it to compress more easily in the cylinder, and potentially improve power and efficiency.
Different cars respond differently to premium fuels, so it may be worth trying it out in your tank, and seeing whether you notice a visible improvement in mileage: If so, you can work out if this justifies the extra cost.
Another difference is that some premium fuels include detergents that can help remove build-ups and blockages in the engine. If you don’t normally use premium fuel, it may be worth filling up with a single tankful occasionally to ensure any build-ups are removed. This will improve the mileage you get when you return to normal fuel.