Ok i got it sorted:
1.) Category: Broad classification of things that fly.
-Airplane, Rotocraft, Glider, and Lighter than air.
2.) Class: Single Engine Land, Multi-Engine Land, Single Engine Sea, Multi-Engine sea, Gyroplane, Helicopter, Airship and Free Balloon.
3.) Type: Refers to a specific make and model of things that fly, including modifications thereto that do not change its handling or flight characteristics, and similarly also for propulsion units.
-Cessna 172, DC-7, B737 - different types of aircraft that fall under the same CATEGORY of airplane; used in the certification of airmen
-DC7, DC7C, and other variants of the DC7 - similar in design, used for certification of aircraft
-JT8D, JT8D-7 are of the same type and then JT9D-3A, JT9D-7 are of the same type; used in the certification of aircraft engines.
So a C172 has a Class of Airplane, a Category of Single Engine Land, and Type of C172-NAVIII or C172SP (different types)
I believe im right, but any one who disagrees can feel free to correct me. After all, we're all still learning to be better aviators
