Neural network models draw their analogy from the organization of neurons in the human brain, and for this reason they are also often referred to as artificial neural networks (ANNs) to distinguish them from their biological counterparts. The key parallel is that a single biological neuron acts as a simple computational unit, but when a large number of these are combined together, the result is an extremely powerful and massively distributed processing machine capable of complex learning, known more commonly as the human brain. To get an idea of how neurons are connected in the brain, the following image shows a simplified picture of a human neural cell:

In a nutshell, we can think of a human neuron as a computational unit that takes in a series of parallel electrical signal inputs known as synaptic neurotransmitters coming in from the dendrites. The dendrites transmit signal chemicals to the soma or body of the neuron in response to the received synaptic neurotransmitters...