This is the Snap Circuits Motor Control IC, or H-bridge. At the top of the figure you can see the electronic schematic of the Motor Control block. On the lower left you can see a picture of the block. The lower center shows the function of each snap for the block and on the lower right is a description of what each snap does. The H-bridge integrated circuit (IC) is easy to use by simply applying power to a particular pin also called "setting the pin high" to drive a motor in one direction. Cutting the power to that pin and applying power to another pin will drive the motor in the opposite direction. The circuitry inside the H-bridge ICs is somewhat complicated, so most folks will choose to use an H-bridge IC rather than building the circuit themselves. The Motor Control IC will also help prevent accidentally sending 9 volts from the Rover’s battery pack through the PICAXE and frying it.
Picture source: http://www.elenco.com/admin_data/pdffiles/SCROV10.pdf