What Causes the ‘Breeze’ Inside a Moving Train?

Imagine you're on a train moving really fast. When the train starts going, the air outside moves slower than the train. This makes it feel like there's a breeze coming from inside the train, kind of like when you open a window in a car and feel wind rush in.

When the train is still, the air inside and outside are the same. But once the train moves forward, the air outside seems to move backward compared to the train. This difference makes it feel like there's a breeze blowing from one side of the train to the other.