Nicotine patches are like square plasters, with lots of very small needles on them. Don't be squeamish about the thought of needles, they are minute, and don't reach the pain sensors under the skin, so you feel no pain. Each of the needles contains a small amount of nicotine. This nicotine goes into the bloodstream, and the smoker's craving for nicotine, which is the main reason they smoke, is theoretically relieved, eliminating the need for a cigarette.