ML or Machine Learning is an AI application (Artificial Intelligence) and refers to algorithms that automatically improve themselves through experience. Those ML algorithms are used where it is hard/impossible to use conventional ones and therefore are applied in various fields. In a business context, ML is often referred to as predictive analytics.
Machine Learning can be either supervised or unsupervised. Supervised ML is task-driven, requiring humans to provide input, desired output, and the variables to be analyzed. Unsupervised ML is data-driven, meaning they are not trained with desired outcomes but use Deep Learning to arrive at conclusions.