The first image is the spool that is leaking.
This image is from the inside of the shower stall. To the right of the handle, you can see the 5/8 in. nut that the top of the spool. This is where the water is leaking from.
This is the the plumbing from behind the shower stall. From this angle, however, you cannot see the spool. But the piece to the left is where the spool screws in on the front (previous picture).