In this video I'm watching then instructor talks about using "jumpers". He's got a motor controller shield and at first he says that "during the making of this video we only had 1 jumper, thus only Pin 4 is working", and that as a result he could only move a motor/wheel in 1 direction.
He proceeds to find another jumper, uses it to make Pin 5 work, and then he can reverse polarity and change the direction the the wheel spins.
At first I thought that he must mean header pins, but when he holds the tiny component up, it looks like it's something else:
I read about a "power jumper" on an Adafruit page, but it only applied to one version of the Arduino and sounded like it was to do with Power joining (using the same power source for the motor and controller), so I really don't know if that's the same thing.