After selecting the object and clicking Rotate, the Command Prompt is displayed in the graphical view.
After selecting  the Specify base point, you are prompted to specify the
Rotation Angle,
Base angle or
Copy.
Selecting rotation angle rotates the object, either clicked in the 3D graphical view or typed as a value.
Selecting Base angle allows you to rotate an object without knowing the rotation angle. For example, rotating a nozzle to line up with another nozzle. The option
Copy is also available during the Base angle command.
Selecting Copy creates a copy of the object at the new position either clicked in the 3D graphical view or typed as a value and keeps the original object at its current position. The option
Base Angle is also available during the copy command.
Back, moves one step back.