As you can see, the rotation tool appears and operates slightly different from the translate and scale tools.
Like translate and scale, you can constrain rotation to a single axis by clicking and dragging any of the three inner rings (red, green, blue) visible on the tool.
You can freely rotate the object along multiple axes, by simply clicking and dragging in the gaps between rings, however you're afforded a lot more control by rotating an object one axis at a time.
Finally, by clicking and dragging on the outer ring (yellow), you can rotate an object perpendicular to the camera.
With rotation, there are times when a bit more control is necessary—on the next page we'll look at how we can use the channel box for precise object manipulation.