'Metatarsals'. Such a lovely word, it rolls fluidly off the tongue. But what are they?
Well, you have five metatarsals in each foot1. The bones in your toes are called phalanges. The bones at the back of the foot, those lumpy things under your heel, are called tarsals. The bones in between are called the metatarsals. If you have occasion to look at a skeleton, they're the ones with more than passing resemblance to chicken drumstick bones.
The proximal end of each metatarsal, also known as the base, is articulated with the tarsal bones. The distal end of each metatarsal, also known as the head, is articulated with a phalanx (the singular of phalanges). Here, as elsewhere in the body, proximal means 'towards the centre of the body' and distal means 'towards the edge of the body'. Incidentally, the big toe is short-changed, having only two phalanges while the rest of the toes have three each.
Soldiers and ballet dancers are prone to fractures of the metatarsals, in both cases presumably related to spending too much time on one's feet. This is not generally a problem for the typical sedentary web surfer.
Of course, human beings are not the only ones to have metatarsals. In birds, for example, the metatarsals fuse together into a solid mass of bone after being separated in the embryo. The archaeopteryx, on the other hand (that famous fossil of a primitive reptilian bird) has distinctly separate metatarsals. Presumably it hadn't learned to fuse them yet.