Neural network weights are adjustable numerical parameters that determine the strength and direction of the connections between artificial neurons across layers in a neural network. During the training process, these values are iteratively modified by optimization algorithms, such as gradient descent paired with backpropagation, to minimize the error between the network predictions and the target outcomes. By scaling the incoming signals passed between connected nodes, weights effectively encode the learned features, patterns, and operational knowledge of the model. Together with bias terms, weights form the primary internal parameters that define how a trained machine learning model transforms raw input data into final predictions.