An identity matrix is a special type of square matrix that plays a crucial role in linear algebra. It is defined as a matrix in which all the elements of the principal diagonal are ones, and all other elements are zeros. For example, a 2x2 identity matrix looks like this: {1, 0, 0, 1}. When any matrix is multiplied by an identity matrix of compatible dimensions, the original matrix remains unchanged. The identity matrix is often denoted by the symbol {I}. It serves as the multiplicative identity in matrix multiplication, similar to how the number 1 functions in regular arithmetic. Identity matrices can exist in various sizes, such as 3x3 or 4x4, and are essential in solving systems of equations and performing transformations in computer graphics.