Definition of a still water fly

I was looking at fly patterns online earlier and I saw some flies that were categorized as still water flies...What are these flies?

Flies that are meant to be fished in lakes, ponds and slow sections of rivers. They are often imitations of organisms that are prevalent in lakes. Chironomids, scuds, damsels, dragons, leeches etc. and certain mayflies and caddis might be included. Of course there is lots of crossover with stream patterns.