The question is;

Find the volume of the solid whose base is the region bounded byy = e^x, y = 1, x = 2 and x = 3 ,

where cross-sections perpendicular to the x-axis are semicircles.

The part of this equation I do not understand is the set up, am not sure how all y=1 comes into play? and how i should revolve this graph to get a solid of revoultion? basically dont know were to start? If anyone please help me with a starting point thank you .