Simply put, ferrous metals and alloys contain iron; non-ferrous materials do not. It may not be easy to tell when just looking at a random piece of metal, but there are several other factors that differentiate the two. Ferrous metals include carbon steel, stainless steel, mild steel, cast iron, and wrought iron. These metals are used for strength and durability, as in skyscrapers, bridges, housing construction, industrial containers, large-scale piping, automobiles, train rails, household tools and hardware, and cooking knives. Most ferrous metals and alloys (with the exception of wrought iron) will eventually rust when exposed to the elements. Their most distinctive characteristic is that they are also magnetic.
Non-ferrous metals include aluminum, brass, copper, nickel, tin, lead, and zinc, as well as precious metals like gold and silver. They are wildly different from each other, but they do have in common that they are usually lighter in weight and more malleable than ferrous metals. Most significantly, perhaps, they are not magnetic.