What is rooftop package air conditioner?

What is rooftop package air conditioner? Just my opinion simply.
1. Sometimes people called it rooftop unit, package unit, RTU, air conditioner mounted on roof......
2. Rooftop package unit in USA has around 20 or 30 years history, because many important, biggest and world-famous AC company in USA, and their AC technology is top and advanced. These years, I think that no more than 10 years, Chinese rooftop air conditioner companys' designing and producing capacity were improved, many Chinese rooftop units have export to Asia, Africa, Australia and Europe and got approved. Shenglin is one of them.
3. Rooftop packaged air conditioners are package units, not split units. Usually they are installed on the roof and ground, so they are outdoor unit. They are direct expansion system, not chilled water system. Usually they are air cooled. As they are package units, so they can be easily installed on roof and just need connect air duct down to the buildings. 
4. Beautiful appearance, stable quality, renowned parts and OEM service. Shenglin, Choose us!
rooftop package air conditioner