Hey Nik,
coopers ringed is basically where each bore has a groove or step machined around it. This then allows a steel 'ring' which I think is about 4mm wide - sort of flat in section, to fit in the groove. This ring actually sits slightly higher than the surface of the block. You need a special gasket to go with these as well, and where the rings are slightly raised exert more pressure on the head gasket, in theory providing a better seal around the bores. I think that's about it. If I have got anything really wrong I'm sure somebody will correct!!