I'll just explain Toyota's flat out.
For example, AE86
A = Engine code, in this case a 4A-GE
E = Chassis, E is used in all versions of the Corolla I can think of
8x = Generation (generally)
x6 = Variation in the chassis.
Some common chassis letters
W = MR2
A = Celica (RWD), Supra
T = Celica (FWD/AWD)
E = Corolla, Prizm, Nova; FWD, RWD, and AWD versions
P = Starlet
Engine codes go like so 4A-GE
4 = Block generation
A = Engine series
- = Separates block and engine series info from details
G = Head, Yamaha in this case
E = EFI
Other letters of interest
T = Turbo
Z = Supercharged
F = Toyota head, economy
U = Carb'd (I think)
I'll get more info as I remember stuff... oh, and add AE82 to the Corolla list (FWD late 80's model) and the AE85 never sold in the US, the SR5 RWD Corollas were also AE86 models.