A transformation from world coordinates (x, y, z) to screen coordinates (pixels). A matrix corresponds to a linear mapping of some vector space to another. In

A transformation from world coordinates (x, y, z) to screen coordinates (pixels). A matrix corresponds to a linear mapping of some vector space to another. In case of graphics you usually start with local coordinates of your object. These have to be mapped to world coordinates, camera coordinates, and finally a perspective projection to get the screen coordinates. All these mappings can be expressed as matrices and applying mapping A after B is the same as applying the matrix product A*B to your initial coordinate vector. Precomputing the entire transformation matrix in this way causes quite a speedup for long transformation pipelines.