Top Bumpstop - Upper Red Circle -
Look at the pic above...look at the top red circled area in the pic...in the lower half of the top red circle there is a black rubber thing sticking up that looks like a half a black rubber ball...thats a bumpstop.
In the same red circle there's a silvery metal thing with a small metal bump pointing down, right above the black rubber bumpstop.
The black rubber bumpstop is fixed in place, and the silvery metal thing (The Upper Control Arm, or UCA) moves up and down as the tire moves up and down.
When the UCA's little metal thing comes down, it will hit the little rubber thing (The bumpstop), which stops it.
So - As the UCA is traveling down, it is travelling down towards the bumpstop...
Lower Bumpstop - Lower Red Circle (Obscured view)-
Similar to the upper bumpstop, but, the Lower Control Arm (LCA) is moving up to hit it, instead of down like the UCA's stop.
So - One (LCA) hits on the way up, one (UCA) hits on the way down.
Hope that helps!