Level 1

Credit score

I realize there are 3 different credit reporting agencies but When I check my score it’s different depending on what online service I’m using for the same credit reporting agency. Why?
Also recently I purchased a car (and before going I checked all 3 reporting agencies scores).
When they pulled my credit at the dealership ALL 3 numbers were different! They told me that they get different numbers that banks and credit unions use, please educate me on this “different” rating numbers used by banks and credit unions. Thanks for any information.