In brief
VIN encodes identification data. Its decoding does not prove by itself mileage, condition or lack of accidents.
Useful to know
VIN is a vehicle identification number. In the American system described by NHTSA, it is 17-character and encodes specific vehicle data. The official decoder can, for example, show a plant and a country of production. [1]
This is different from a history of use. The fact that the number has been decoded is not in itself evidence of actual mileage, repairs or lack of accidents.
Practically use decoding as a single compliance check: whether the underlying data presented is logically related to the particular vehicle. For additional history, other records and viewing are required; do not attribute to the decoder information that he has not shown.
On older vehicles and different markets, do not unconditionally apply any rule to a modern American VIN. The material explains what the stated official tool does, rather than certifying the origin of a random car by one introduced sequence.
Sources
For further detail and to check the information: