Linear systems is a branch of mathematics and engineering that deals with systems of linear equations and their properties. These systems can be represented in matrix form and studied using various techniques such as Gaussian elimination, matrix algebra, and eigenvalues/eigenvectors. Linear systems theory is widely used in control theory, signal processing, communications, and other fields to analyze and manipulate systems with linear behavior. The study of linear systems also involves concepts like stability, controllability, observability, and feedback control. Overall, linear systems provide a foundation for understanding and analyzing complex systems in various scientific and engineering disciplines.