What is the scum gutter of an above ground pool 18' by 18'?

I may be wrong but I doubt there is a scum gutter on above ground pools. There may be what is called a skimmer and that is sort of a hollow box like object at one side of the pool - usually located closer to the pool equipment side of the pool. When the pool pump is running you will be able to see water entering the box or skimmer. The purpose of the skimmer is to catch bugs, leaves, etc and to get the water back to the pump. It is part of the circulation system.