The stress-energy tensor is a mathematical object used in physics to describe the distribution of energy, momentum, and stress in a given region of space and time. It encapsulates how matter and energy influence the curvature of spacetime, which is a key concept in Albert Einstein's theory of general relativity. This tensor has components that represent various physical quantities, such as energy density, momentum density, and pressure. By understanding the stress-energy tensor, scientists can predict how objects move under the influence of gravity and how energy flows through different systems in the universe.