What is Business Class?

Legal Definition
Business class is a travel class available on many commercial airlines and rail lines, known by brand names which vary by airline or rail company. In the airline industry, it was originally intended as an intermediate level of service between economy class and first class, but many airlines now offer business class as the highest level of service, having eliminated first class seating. Business class is distinguished from other travel classes by the quality of seating, food, drinks, ground service and other amenities. In commercial aviation, full business class is usually denoted 'J' or 'C' with schedule flexibility, but can be many other letters depending on circumstances.
-- Wikipedia
Legal Definition
Also known as executive class or upper class, is a high quality second-tier travel class available on some commercial airlines and rail lines. Its level of accommodation is higher than economy class and domestic first class but lower than international first class.