A person is sitting inside a train (Train A). The train has not started moving yet. When that person looks out the window, they see another train (Train B) . Both trains are facing the same direction. If Train B moves backwards, it appears to the person on TRain A that they are moving toward Train B. If a reference point it added this can be changed. If the person can also see a pole next to the trainsm they will see that train A did not move and train B moved backwards.