Bent over row

Hold a dumbbell in each hand, and hinge at the hip (just like a deadlift), so your bum is backwards but your back is flat. Then, with the weights dangling directly under your shoulders, pull them up towards your chest, keeping your elbows tucked in tightly. Slowly lower the weights back down, and then repeat.

Demi - what does this mean . . .?
"Hinge at hip" and
"your bum is backwards"

Of all the exercises listed, this looks like one I can do. All the others require good knees.