Angle Class 1 type 1 maloclusion
first molars are well aligned, crowding in incisive arc.
Angle Class 1 type 2 maloclusion
first molars are well aligned, lower incisives inclined inside.
Angle Class 1 type 3 maloclusion
first molars are well aligned, anterior crossbite.
Angle Class 1 type 4 maloclusion
first molars are well aligned, posterior crossbite.
Angle Class 1 type 5 maloclusion
first molars are well aligned, posterior crowding.
Angle Class 2 division 1
Lower first molar is back from where it should be, superior incisives are inclined toward the front.
Angle Class 2 division 2
Lower first molar is beside from where it should be, superior incisives are retroclined toward the back.
subdivision mean the class 2 is unilateral.
Angle Class 3
Lower first molar is advanced compared to where it should be.
Note: the normal position of the first molar is: the mesiobuccal cuspid of the first superior molar occlude on the buccal fissure of the first lower molar.
Wikipedia has a great starting point for your project with photos describing Angle's Classification of Malocclusion. Besides what the dentist told you, Class III malocclusions can be dental or skeletal.