Compose = How you want your final image to be. i.e You choose the angle, subject etc to be inside ur frame and Snap it.
Focus = Sharpness on the part of ur subject that you want it to be sharp. i.e You can manual focus, autofocus with autoarea, or you can manually select one of the 7or9or11 to be your focus point which ur camera will focus on it with sharp detail. For portrait, you will need the eye to be sharp.