A matrix is a rectangular array of numbers, symbols, or expressions, arranged in rows and columns. The size of a matrix is typically denoted by m×n, where m is the number of rows and n is the number of columns. For example, a 3×4 matrix has 3 rows and 4 columns.Matrices are often used in mathematical and scientific calculations, because they can be used to represent complex relationships between data sets. For example, a matrix can be used to represent the coefficients of a system of linear equations.Matrices can also be used to represent geometry, such as points in space or transformation matrices. In computer graphics, matrices are used to represent images, because they can be used to store pixel information.There are many different types of matrices, depending on the operations that can be performed on them. The most common type of matrix is a square matrix, which has the same number of rows and columns. Other types of matrices include triangular matrices, diagonal matrices, and lower triangular matrices.