A neural network is a set of algorithms that mimics the functioning of the human brain to recognize patterns in data. It is a powerful tool that has revolutionized the field of machine learning and artificial intelligence, and can be used for a wide range of tasks, from image and speech recognition to natural language processing and even game playing. A neural network is made up of layers of interconnected nodes, known as neurons, which take input from neighboring neurons, process the information, and pass the output to the next layer. Training a neural network involves feeding it an input dataset and adjusting its parameters to optimize its performance on a specific task.