Matrices are rectangular arrays of numbers or symbols arranged in rows and columns. They are used in various fields of mathematics, science, engineering, and computer science to represent and manipulate data, equations, and transformations. Matrices can be added, subtracted, multiplied, and transformed using various operations and algorithms. They are also used to solve systems of linear equations, find eigenvalues and eigenvectors, perform linear transformations, and represent graphs and networks. Matrices are an essential tool in many areas of modern mathematics and its applications.