A neural network is a network or circuit of neurons. The neural network has layers of units where each layer takes some value from the previous layer. That way, systems that are based on neural network can compute inputs to get the needed output. The same way neurons pass signals around the brain, and values are passed from one unit in an artificial neural network to another to perform the required computation and get new value as output. The united are layers, forming a system that starts from the layers used for imputing to layer that is used to provide the output