Firewood is sold by a measurement called a “cord."  A cord must equal 128 cubic feet. To be sure you have a cord, stack the wood neatly by placing the wood in a line or a row, with individual pieces touching and parallel to each other, making sure that the wood is compact and has as few gaps as possible. Then measure the stack. If the width times the height times the length equals 128 cubic feet, you have a cord of firewood!

Generally, your greatest variety of firewood types are available at yards like Mr. Yard which specialize in firewood sales. The type you buy depends in part on what you intend to use it for. For a fireplace generally any hardwood will do. Softwoods are generally cheaper but they burn cooler and faster. They do make good kindling though because they ignite very easily. Be sure you are buying seasoned (dried) firewood because fresh wood is wet and does not burn well.