Schemas are groups of objects in s-Server, including streams, tables, and so on. All StreamLab objects--guides, external connections, sinks, sources--represent one or more of these s-Server object. A sink, for example, consists of a pump and a stream.
When you create a new source, external connection, sink, or guide, StreamLab uses the project schema by default. Using the project schema makes it easier for other s-Server developers to access the objects you create in StreamLab.