by Chris Tyler:
Fundamentals: Object Types » Primitives
This fundamentals tutorial shows what primitives are and how to create them. Note: Design 3D CX interface is shown but the operations are the same for SE.
Any Primitive Tool + Shift: Create primitive constrained. (video 1, 1:30)
Any Primitive Tool + Option: Create primitive from center. (video 1, 2:04)
Any Primitive Tool + Shift+Option: Create primitive from center and constrained. (video 1, 2:15)
This is a simple tutorial for new users.
If you want more basic information about primitives, watch the following video.