The "nearest neighbor" algorithm is a simple method used in various fields, including machine learning and data mining. It works by finding the closest data point in a dataset to a given input. This is often done using a distance metric, such as Euclidean distance, to measure how similar or different the points are. In practical applications, nearest neighbor can be used for tasks like classification and regression. For example, in image recognition, the algorithm can identify an image by comparing it to a database of labeled images and selecting the one that is most similar.