A machine learning model in AI applications refers to a computational algorithm designed to analyze data patterns, learn from them, and make predictions or decisions based on new data. It uses statistical techniques to improve its accuracy over time without being explicitly programmed for each task. Models are trained on diverse datasets and can be applied in various fields such as healthcare, finance, and marketing to automate processes and gain insights that aid decision-making. The efficiency of these models often hinges on the quality and quantity of data they are trained on.