This is a rather intriguing aspect to some self-propelled models in that they can sometimes mow backward. While you can’t expect every model to be able to do this if they do it can assist with the mowing process as this does not limit you. In some instances, it will be much easier to simply back up the mower to cut a specific piece of grass you missed or to cut grass that is an awkward area.
If the engine of the mower does not have a self-drive system, though, this may only be achievable by pulling and releasing the drive lever. Seeing as this would not be something you would most likely be using often, do not fret about it too much.