How to get displayed object's vertices in a Buffer ?

I displayed a 3D object in a window by specifying coordinates in glBegin() and glEnd().My question is how to get the x,y and z values of the object from the window in a mouse click.
Is possible ?I read that glFeedbackBuffer will returned it.If so,it is contain ogl coordinates or screen coordinates ?Anyway to get ogl coorinates ?

Pls specify the steps to follow or any helping code

Thanks a lot,

Do you want to pick vertexes ??? If so just do a search on the web for selection buffer or glproject, or give a visit at Romka’s web site. he has some good picking tutorials.