This is a very very simple robot, it only moves forward and has no controls other than a rudimentary on/off switch.
Despite it's simplicity and lack of usefulness as a combat or service robot, it is a fun toy and you can make it with very common parts.
You will need:
-Two low voltage motors.
-One AA or AAA battery.
-One on\off switch.
This isn't really meant for people who have a ton of experience in robotics, its meant as a simple little toy you can make from really common components.
Step 1: Wire Up the Circuit.
Attach the wires, motors, the battery and the switch as shown in the diagram above.
Naturally, if you have experience with electronics you could set it up differently so it would do something more specific.
Step 2: Glue/tape It All Together.
Glue or tape the motors onto the battery, and the switch to the top. With both motors touching the ground and the battery being dragged behind, the car will move forward. If the machine will not move forward, add rubber, pencil erasers, glue, electrical tape, or anything that will make it more "grippy" so it moves forward easier.