The stress tensor is a mathematical construct used in physics and engineering to describe the internal forces within a material. It provides a way to quantify how forces are distributed across different points in a solid or fluid. The stress tensor is represented as a matrix, with each component indicating the intensity of stress acting in various directions. In the context of continuum mechanics, the stress tensor helps analyze how materials deform under external loads. It is essential for understanding phenomena such as elasticity, plasticity, and fluid dynamics, allowing engineers and scientists to predict how materials will behave under different conditions.