RFID stands for "Radio Frequency Identification" and refers to reading radio signals from a distance. It is a technical system that allows data to be read without contact. Since almost all credit and debit cards nowadays contain chips for so-called contactless payment, it is also possible to protect against unauthorized reading of sensitive data. The I-CLIP RFID Blocker Card Set, consisting of two cards, protects up to 10 credit, bank, EC and ID cards as long as such are sandwiched between the two RFID blocker cards. Cards that are outside the two cards can still be read as usual (such as a time card).
For more details on how these work checkout this video click here