Can someone give me a quick overview of how geograph works and how the images are taken?

I ask this because a number of images from my home town are poor quality, and incomplete (I can locate less than 5 notable buildings photographed in the town, when the real number is circa 20-30). 

When I say "poor quality" I don't necessarily mean low res etc. but of poor photographic quality; for example a monument in the centre of the town is photographed from about half a mile away across the roofs of several buildings (although you can drive/walk right past it...).

Tom