!the environment flips around the load
To reverse the direction of a DC motor, one must reverse the direction of the current flowing through it. But the motor itself is bolted down; it cannot be physically turned around.
The H-bridge resolves this by leaving the load perfectly static and flipping the entire electrical environment around it.
It surrounds the load with four switches, arranged like the vertical legs of an 'H' with the load as the crossbar. By closing the top-left and bottom-right switches, current flows down through the load from left to right. By opening those and closing the top-right and bottom-left switches, the path is mirrored. The current now flows down through the load from right to left.
The load never moves. The structure simply reconfigures the universe around it, making "forward" and "backward" a matter of which diagonal path is currently permitted to exist.
