Bias Unit? Noob Question. • /r/MachineLearning

I'm working my way through the Coursera course on Machine learning by Andrew Ng, and I'm really confused about the bias unit? In the programming assignment, we always set the parameter for the bias unit to 0, so how does it affect the neural network in any way? Since the bias unit will be multiplied by it's parameter/weight (which seems to always be zero), wouldn't it be completely insignificant?