An artificial neural network (ANN), often just called a "neural network" (NN), is an interconnected group of artificial neurons that uses a mathematical model or computational model for information processing based on a connectionist approach to computation. In most cases an ANN is an adaptive system that changes its structure based on external or internal information that flows through the network.
(The term "neural network" can also mean biological-type systems.)
In more practical terms neural networks are non-linear statistical data modeling tools. They can be used to model complex relationships between inputs and outputs or to find patterns in data.
A neural network is an interconnected group of nodes, akin to the vast network of neurons in the human brain.
More complex neural networks are often used in Parallel Distributed Processing.