with standard twist drills, HSS are hard enuff for anything, HS or carbon steel bits are generally wood only, but I think uncommon - the particular angle of the point determines best use for metal types
check here otherwise, there are a variety of bit types for wood only, like augers, forstner bits and the flat bladed wood bores - there's also bits for concrete/masonary w/ odd looking "winged" points
Bill
