Image plane or vector rotation matrix to camera center about coordinate axes?

Question

Mathematics

Again, the question is because of this article .

3 × 3 internal camera parameters matrix (a specific view is given below), R is a 3 × 3 orthogonal matrix that determines the rotation of the camera relative to the global coordinate system.

Question: Does this matrix express the rotation angles of the image plane relative to the coordinate axes, or is it the rotation angles of the vector pointing to the camera center relative to the axes?

(The black line is the projective plane of the image; the black dot is the center of the camera; the blue line is the vector that points to the center of the camera; the green and red lines are the coordinate axes)

Answer 1

First. That is, in which direction the lens is looking and how it is rotated around its axis.
The second one (a pointer to the center of the camera) is the vector c.