You may have footage that has an inverted alignment of the camera, which is quite common if you receive footage from an action camera. For instance, you may receive footage from an action camera using a windshield mount in a car. To better align the footage, the operator sets it upside down.
That footage will also be upside down. You will have to flip it to use in your project.
Blender has an option that will enable you to flip video in the X (Horizontal) or Y (Vertical), as Figure 3.7 shows:
Figure 3.7: Flipping options
The flipping process is simple and doesn't require any additional settings: pick the axis and Blender will invert the video or image.