what's in a Hub?

Well in the beginning I hardly noticed this mysterious piece of metal… And now I want to know!

what’s in a hub? any link to drawings, exploded views?
how are those made, machined? with which metal?

what makes a good hub … and a better one?

thanks

bear

which type of hub, square taper of splined? genreally square taper are a single axle with the spoke flanges welded on, splined have a solid splined axles made of heat treated steel with an aluminium body splined or keywayed on to it.