Thanks to PHPdeveloper for pointing out this great article.
An artificial neural network is a model of the organic brain. It attempts to reproduce the interactions between the neurons in the brain during the learning and thinking process. It works by applying mathematical formulae obtained from medical studies of how the actual brain works.
There are several different types of ANNs. This implementation will model the feed-forward, multi-layer neural network. An ANN learns in the same way as the natural brain, that is, by reinforcing the connections between neurons. Several learning (or training) algorithms have been devised.