Also, just like the other tools, Google drawings can be shared with other Google Docs users, allowing multiple users to collaborate on a single file. That means, one can draw the eyes, another the ears, still another the mouth. Not sure why you'd want to do that though. Anyway, here's a quick Google doodle I made using my laptop's touchpad a couple of minutes ago.
Click on the image to enlarge.
Like the other tools, the features on Google Drawing are pretty limited. However, you can be sure they've integrated the most widely used ones. For instance, there's a freehand tool (named scribble), which I used to draw the head. That cloud was a vector graphic (that means, it can be resized) I grabbed from their Shapes collection.
There are tools for drawing lines, arrows, and polygons, as well as tools for changing the fill and outline colors. You can also change the width and style (e.g. dashed or solid) of the drawing/outline tool. As you can see, you can also add text.
This new addition to the Google Docs suite can come in handy for drawing simple figures. Not sure if we can copy and paste the figure to a Google Docs document though. Will try that next time.