The sigmoid function is a mathematical function that produces an "S"-shaped curve. It is commonly used in statistics and machine learning, particularly in logistic regression and neural networks. The function maps any real-valued number into a range between 0 and 1, making it useful for modeling probabilities. In the context of artificial intelligence, the sigmoid function helps in decision-making processes by transforming inputs into outputs that can be interpreted as probabilities. This characteristic allows models to predict binary outcomes, such as yes/no or true/false, effectively aiding in classification tasks.