I think the card you have is RFID enabled. They've been around for a while, and have some weaknesses (replay attacks [1], notably), against the ID they broadcast when inside an EM field.

The newer cards have a microprocessor inside them, with exposed contacts about 10mm from the left edge. With chip + pin transactions, the pin "unlocks" the payment authorization [2].

[1] https://www.chicagofed.org/digital_assets/publications/econo...

[2] http://en.wikipedia.org/wiki/Chip_and_PIN