Alloy steel is steel mixed with elements like chromium, nickel, molybdenum, and manganese to enhance desired properties for specific applications. Each element improves a specific attribute in steel like hardness, toughness, durability, corrosion resistance, and many more. For example, carbon steel is a subset of an alloy steel, so there can be varying levels of an element added to the mixture (high, medium, and low). It's generally used in the automotive and constructure industry and is available in various shapes such as sheets, coils, bars, and plates, as well as in different grades for specific properties.