Found this explanation.
A (VIN) Vehicle Identification Number is designed to define major components of a vehicle such as engine, transmission, differential ratio, year, make and model as well as a unique identifier foe the vehicle on which the VIN tag is securely placed.
1 Position number one represents the country of origin or the final point of assembly. Some examples of the different codes are: 1=U.S.A., 2=Canada, 3=Mexico, J=Japan
2 Position two identifies the manufacturer.
3 Position three identifies the vehicle make.
4 Positions four through eight are unique vehicle attributes such as the transmission, rear end ratio, steering, etc. These attributes designate the model of the vehicle.
5 Position nine is always the check digit. This position will always be numbers 0 - 9, or the letter X. The check digit is a mathematical formula that allows the detection of an invalid VIN.
6 Position ten is the model year. This position always contains a letter from B-X (except l, O and Q). B starts with the model year 1981 and X ends the year 2000. So, if someone claims their vehicle is a 1991, you can verify it by checking to see that the tenth character is the letter M. B81, C82, D83, E84, F85, G86, H87, J88, K89, L90, M91, N92, P93, R94, S95, T96, U97, V98, W99, X00. Don't ask me what they are going to do at the turn of the century!!
7 Position eleven identifies where the vehicle was assembled.
8 Positions twelve through seventeen are sequential production numbers. Each manufacturer uses the last six characters differently, so there are no specifics for these positions.