A metric tensor is a mathematical object used in geometry and physics to define the distance between points in a space. It provides a way to measure lengths and angles, allowing us to understand the shape and curvature of that space. In the context of general relativity, the metric tensor describes how gravity affects the geometry of spacetime. In more technical terms, the metric tensor is a symmetric, bilinear form that can be represented as a matrix. It varies depending on the coordinates used and can be used to calculate important properties like curvature, which is essential for understanding the behavior of objects in curved spaces or manifolds.