What is that part in grey called?Window frame?
What is that part(which is protruded) function and isit necessary to have one around the window?
Im going to extend that wall,so thinking to get rid of it which i dont think have any function.
And that window is really tall,i wanted to replace with a smaller one......slider one is on my mind right now.
Any other recommendations?

Hello .. which window-frame is better .. aluminum or power-coated material? Stainless steel looks ugly .. i believed Aluminum is more expensive but the color will degrade .. any comments?