what is the difference between ODOMETER and SPEEDOMETER ???
Odometer measures the total distance covered by a vehicle. The reading of an odometer always increases. Suppose your car was showing 2150 Km in its odometer. You travel to a nearby town and observe that the new reading is 2250 Km. The distance you covered to reach the town is (2250 - 2150) = 50 Km & the total distance your car has travelled from the day you bought it is 2250 Km.
Speedometer measures the speed of the vehicle at any instant. When your car is not moving the speedometer will show 0 Km/hr. When it begins to move it may show 10 Km/hr. You put it in 3rd gear and after some time you may see 50 km/hr. If you apply brakes you will observe that the pointer of the speedometer is moving towards the zero. Reading of a speedometer always fluctuates or changes depending on the way you drive the car. It may momentarily show a constant speed if you drive with a constant speed.
I’ve highlighted the differences in bold letters.