Screen direction refers to concept of cinematic grammar which involves the direction that characters appear to be moving on the screen from the point of view of the camera or audience.
If a character exists a frame from going from right to left, he should enter the next frame from right to left if we would like the audience to understand that he is headed in the same direction.
If we disobey this simple rule and have the character exit frame left and enter the second frame from the left, the character seem to have made a U-turn.
We should pay attention to screen direction grammatical rule in the last shot.
Meaning if we covered a character starting going from right to left, it should enter the frame of its destination from right to left.