A corn cob is the inner core of an ear of corn. They were once simply discarded as a waste product. Corn cobs have found to have many uses in more recent years.
I've seen reference to using corncobs as:
and from the blog of Chadzilla:
"I know many chefs are on to the benefit of boiling corn cobs for stock, but they really are incredible. They can be used for maximizing corn flavor in foods as opposed to the traditional uses as substitutes for toilet paper and building material for tobacco pipes (aye, popeye). Recently, I pressure-cooked some cobs at home to make a foundation broth for a corn cilantro soup and fell in love with the idea again."