OpenGL: What is MatrixMode?

OpenGL uses several matrices to transform geometry and associated data. Those matrices are:

Modelview – places object geometry in the global, unprojected space

Projection – projects global coordinates into clip space; you may think of it as kind of a lens

Texture – adjusts texture coordinates before; mostly used to implement texture projection (i.e. projecting a texture as if it was a slide in a projector)

Color – adjusts the vertex colors. Seldomly touched at all