"拓片" (tàpiàn), or inscription rubbing, is the process by which you transfer the text from a inscription on a stela to paper.
First you tightly paste a piece of wet paper on the stela, dry it with a fan, then you rub black ink on top of the paper, leaving the engraved text as white, thus making a copy of the inscription that's much more readable than the stela itself.
One of the most famous stela being the record of Nestorian Christianity in China, dating back to the 7th century (Tang dynasty). It's the earliest known biblical text in Chinese, carved in stone, and discovered after over a thousand years. If you come to Xi'an Beilin ("stone forest") Museum you can see it for yourself, and you can purchase your own copy of the rubbing from nearby stores, or order one from Taobao. A friend of mine just bought a copy of the Nestorian stella for 150RMB, rubbed from the original stela! It's like holding a piece of ancient history in your hand, absolutely priceless.
I hope more people will appreciate this art form and see its value.