Object Mode and Edit Mode
In Object Mode, the Add Grease Pencil menu provides three different Grease Pencil primitives:
Adds a Grease Pencil object without any stroke.
Adds a Grease Pencil object with a simple stroke as a reference.
It creates a 2D monkey head. The Monkey's name is "Suzanne" and is Blender's mascot. 2D Suzanne is very useful as a standard test.
Materials and 2D Layers
Adding Stroke or Monkey primitives also adds a set of preset materials and 2D layers to help start drawing with the new object.