They brought 841 pounds of the Moon back with them. Apollo Moon samples range in size from sand and pebbles to basketball-sized rocks.
Moon rocks are completely different from rocks native to Earth.
Their mineral content is unique and they show distinctive signs of exposure to the solar wind, cosmic rays and meteoroid impacts. To a trained geologist there's no mistaking a Moon rock. But you don't have to take the word of an expert. There are museums in the United States where you can inspect Moon rocks for yourself and see the distinctive meteoroid impact pits that pepper nearly all rocks from the Moon. Every single researcher agrees that the Apollo Moon rocks are genuine.