A marking session can be considered as a 'state of interaction' that the user holds with the Gild Marker View and the Eclipse workspace. This state describes the scheme that the marker is using, the things that he or she is marking, and the marking data that can be applied to those things.
The "things" that are marked using the Gild Marker View are projects (and the resources contained therein) in the Eclipse workspace.1 The data applied to the projects and resources are called marking (line) notes.