What are the differences in these two types !!?!??!
glMatrixMode(GL_MODELVIEW);
glMatrixMode(GL_PROJECTION);
There are 3 Matrices and so there are 3 matrix stacks, one for projection, the other for model view and the last for textures. glMatrixMode determines which matrix stack you are going to deal with when you call glPushMatrix, glPopMatrix, glRotate, glTransfere, glScale, glMultMatrix, glLoadMatrix, …etc. Vertices are first multiplied with the modelview matrix and then with the projection matrix. Use projection matrix to choose a type of projection (i.e. perspective (frustum) or parallel (orthogonal)) and to do transformations related to eye/camera position and orientation, and use modelview matrix to do transformations on the objects you want to render. Remember, modelview matrix stack is larger than projection matrix stack.