glrotate geometric question

hi! I have a simple question… How is glrotate calculated? I know that it multiplies a matrix ecc… but pratically, if I draw a rectangle, and I rotate it, the rotation is calculated between the center of the object and the origin , between one angle of the object and the origin or what?

The rotate function just “adds” a rotation matrix to the transformation chain, so the rotation will be around the current zero (coordinate system center).