Technically a rectangle is just a combination of four lines with automatic relations
2xVertical
2xHorizontal
4xCoincident
You could generate the entity with lines and relations, but this tool is much quicker
NOTE: If you want an equally sized rectangle (a square) and/or you want it angled, you'll use the POLYGON tool
Tools→Sketch Entities→Center Rectangle
LMB Origin→LMB Elsewhere in Graphics Area
Center Rectangles are useful when Symmetry is a factor in your design
If your first point is the origin on the Front Plane, the Right Plane shall be centered perfectly
NOTE: Center Rectangle also include diagonal Construction Lines and a center Point
Tools→Sketch Entities→Corner Rectangle
LMB Origin→LMB Elsewhere in Graphics Area
Corner Rectangles are a General-Use Rectangle
In the Property Manager (where the Design Tree normally is) the Rectangle Type selection options will appear
You may swap between rectangle types here
The 1 & 2 icons indicate where your first and second LMB will anchor the points
Corner and Center Rectangles have a few Relations such as the Horizontal and Vertical Lines around the perimeter of the entity
To Show Relations:
LMB Hide/Show Arrow→LMB Relations Icon