Partial least squares regression (PLS) is a way of looking at a set of numbers and predicting what will happen in the future. It uses a technique called 'regression' which helps people to figure out what might happen based on what has happened before. With PLS, you take two sets of numbers and put them together to figure out how the first set of numbers affects the second set. This lets you predict what will happen in the future if the first set of numbers changes.