In-Line Skimmer and pump set up

[sgc0286]

Hey! So when I bought my tank it came with a sump, skimmer, and pump. It is all an "in line" set up. Im not quite sure how it works, so if someone can run me through that it would be a great help(I wont be using it myself, but I would like to be able to explain it to whoever buys it) The main thing is the small black piece in the second picture; is that a pump? Where does it go? Thanks..

[ccCapt]

It looks like a pump. Drop it in the left section of the sump.

[sgc0286]

I thought it was a pump. JW what do you think I should sell this for? Pump is pondmaster 950gph(100new), Sea Clear skimmer(not sure on rating, was used in 130gal), Amiracle sump.