You put it between two pieces of paper, then you write on the top one and it creates as copy on the bottom one.

你将它放在两张纸之间，然后你在上面那张纸上写字,下面那张纸上就会复印下来。

耶鲁公开课 - 金融市场课程节选

I like books. I'm old-fashioned. I like the paper copy, you know.

我喜欢书籍。我是个守旧的人。我喜欢纸质的书。

美国的出版市场 - SpeakingMax英语口语达人

He speaks in a language of math and it is very important for students to be able to have hot copies so that they can take notes on the paper rather than be working very hard to copy down the equations that he used in these lectures.

他以数学语言授课,所以发给学生教学材料,是非常重要的,这样就可在纸上做笔记,而不用拼命,抄下他在课上,用到的等式。

麻省理工公开课 - 媒体、教育、市场课程节选