The odometer in your car tells you just one thing – the number of miles on the engine. This is critical information, and is necessary for a very wide range of things, from the title of the car (if you sell the car, you’ll need to note the accurate mileage) to service intervals. The odometer cannot be reset and tampering with it is a crime.
You also have two trip meters (A and B). These are used to measure the mileage of specific trips. Both trip meters can be reset to 0 so you can accurately track mileage when necessary and then clear it when you no longer need that information.