[SturgeonsLaw]

http://ecx.images-amazon.com/images/I/51bClUYQTPL._SL1000_.j...

They take an imprint of the embossed credit card details for later processing

[dylz]

What is there to imprint? Most cards I see dont' seem to have raised lettering; it's just printed numbers on the back.

Also, how does this work with chip-required cards?

[kalleboo]

This system was most commonly in the 90's and earlier. Back then all cards had raised letters. Many modern cards are online-only to reduce the rampant fraud possible with this old method.