Can anyone tell me what a macular scar is?

It is a scar. In the central portion of the retina. Scars can be from many causes which are often not evident when the scar is found. Depending on the location within the macula and its size, a scar can cause mild to severe loss of vision.
Macular scars. The macula is a small oval spot in the center of the retina, where photosensitive cells line the back of the eye. It is the macula that is responsible for sharp, detailed vision and for what you see right in front of you. It is usually a result of end stage wet macular degeneration or choroidal neovascularization (vessels) which impede vision in central gaze. Produces a central blind spot.