A sparse array is a data structure that efficiently stores data when most of its elements are zero or empty. Instead of allocating memory for every element, it only keeps track of the non-zero values and their corresponding indices. This approach saves memory and improves performance, especially in applications where data is mostly unoccupied. Sparse arrays are commonly used in fields like computer graphics, machine learning, and scientific computing. For example, in machine learning, they can represent large datasets with many missing values, allowing algorithms to process data more efficiently without unnecessary memory usage.