The thumbs help! Our proportions are more suited for dexterity if I want to be technical, since the thumbs are comparatively reduced and the metacarpals lengthened in apes that do still live in trees, but the phalanges do come into it. It's easier to illustrate with charts or skeletons— which I totally have a full set for! I have dragon, lizard, deer, and cat bones if you ever want a full demo.

But basically what's your claws is what would be the first digit of our fingers. Our nails protect our fingertips and provide a stiff surface for scratching, grooming, or other work. it's like having a pair of tweezers around all the time!