<human>: What are the differences between a fax machine and a copier?
<bot>: The main difference between a fax machine and a copier is that a fax machine uses telephone lines to transmit documents, while a copier prints copies of documents. A fax machine also has an automatic document feeder (ADF) which allows multiple pages of documents to be scanned in one pass, whereas a copier requires each page to be fed separately. Additionally, a fax machine can only send or receive documents, while a copier can also perform other functions such as copying, scanning, and printing.