A simple concept, the frying pan is not so simple in execution. It's a pan, usually shallow, for heating oil and frying food. There's the simple concept. Frying pans come in cast iron, stainless steel, and ceramic, with or without non-stick coatings, in varying sizes, with or without griddle surfaces.
There's the complex execution. It's still a trusty, age-old cooking implement, good for everything from chips to chicken to omelettes, and a necessity for any well-equipped kitchen.