Hi,
Good question
VIN (Vehicle Identification Number) is a code that contains essential characteristics of a certain car. More detailed information you can find
here. There are lots of services with the help of which you can learn the data on your vehicle. For example,
http://www.dmv.org/vehicle-history.php,
https://www.nicb.org/theft_and_fraud_awareness/vincheck,
https://www.carfax.eu/free-vin-decoder or any other you like.
The main purpose of VIN is to make vehicle identification. With the help of VIN checking you can find out a general information on your car, its history (records, damages, recalls, etc.) and many other information. You need the VIN for searching the right spare parts as well.
Hope I was able to answer your questions. If you have something else to ask, don't hesitate!