Neural Network
A neural network is a machine learning model loosely modelled on the structure of the brain, built from layers of connected artificial "neurons" that learn through training to recognise patterns in data.
In practice
Neural networks are the technical foundation of modern language models and image recognition systems. For working with AI tools in practice, the important thing is to understand that a language model does not look up a fixed answer but calculates a probability distribution over the next word – and that the output is then drawn from that distribution at random. The calculation itself runs deterministically: the same weights and the same input produce the same result. The variation only arises when the next word is picked, steered by settings such as temperature or top-p. That is why the same prompt can produce slightly different answers.