VIN (Vehicle Identification Number) is a number assigned by the automaker as a unique identifier of a car/model. The numbers are assigned based on an ISO 3779 - 1983 standard which allows for universal identification worldwide.
WMI - international identifier of the automaker - It is based on 3 numbers/letters.
VDS - description of the model - It is based on 6 characters and gives the description of the model in a sequence selected by the manufacturer.
VIS - unique auto identifier - These are the last 8 characters (last 4 are usually numbers) and almost always include the year of production and the manufacturing plant.
VIN is made up of alphanumeric characters, with last four almost always being numbers. They could make any combination composed of these capital letters and numerals: 1 2 3 4 5 6 7 8 9 0 A B C D E F G H J K L M N P R S T U V W X Y Z.
The automakers will often separate the elements of VIN's, WIM's and VIS's with blank spaces or other punition marks but in the auto's documents VIN must appear as one string without any spaces or interruptions, the same is true for VIN's visible on/in an auto.
Material based on ISO 3779 (1983)