A woodpile is wood stacked up in one place, waiting to be burned — usually cut logs kept outside a house, by the wall or under a small roof, ready for the fireplace or the stove in winter. It is one word, and it means the whole pile, not one piece. This is an everyday word in cold countries where people heat their homes with wood, so it appears a lot in stories about farms, cabins and country life; in Taiwan most students meet it in reading, not in life. It carries a quiet feeling of preparing for winter. There is also a fixed old phrase, 'a snake in the woodpile' (or in American English, 'the something in the woodpile'), meaning a hidden problem you don't see until you reach in — but the older American version has a racist history, so I would tell students to understand it if they read it and not to use it themselves.