What parts do

What parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts doWhat parts do