The "chip" in your card is called a RFID (Radio Frequency ID) tag. They have a lot of neat uses, but some potential privacy infringing uses as well. Skimming is where someone takes your card out of your sight (like when eating someplace and they take your card from you while at the table and go ring it up) and they run it through a handheld device that allows them to copy the info on your card and fradulantly copy the info to a blank card. Google both if you want to learn more.