Normally, when referring to a business jet aircraft, you will find that these aircraft are small sized and are especially designed to transport small groups of people (usually not more than 19 people). People that own and fly in such aircraft are normally business people as well as the truly well off individual.
A business jet aircraft is all of that and more. It is also an aircraft that can be adapted for different uses other than transporting business persons and rich people. It can, in fact, also be used for evacuation of casualties and it can also be used for delivering parcels in quick time. It is also used by the government and by the armed forces as well as by public bodies.
Most such aircraft will be powered by 2 or 3 engines though in a few instances, they might even be powered by four engines. However, with improvements in reliability of the modern aircraft engine, the need for a four engine aircraft is much less today as three and two engine aircraft can do the job admirably well.
Today, the demand for light jet aircrafts has grown tremendously and the same is the case for personal jets. This demand has resulted in production of single engine jet aircraft instead of four engine jets which have in fact become more or less redundant. Engines are normally rear mounted and not mounted on the wings. There is a reason for this; since the wings of jet planes are not very high from the ground, it does not make sense to mount the engines there and this is why they have to be mounted at the rear.
Today, there are about 11000+ business jet aircraft being operated in different parts of the world. Most are used in the US followed by Europe and other countries where these jets are used include Middle East countries, Asia and Central America.
Such aircraft are not being manufactured in very large volumes which means that if you order one today, it will only delivered to you in a couple of years time.