Nicotine replacement therapy or NRT is one of the most common methods of quitting smoking. In simple terms, any form of NRT is supplying the body with nicotine in a form different from smoking it. The idea is that over time you will break the habit of smoking while at the same time getting used to lower and lower levels of nicotine. Quitting smoking is both psychological and chemical. By gradually instead of suddenly lowering the amount of Nicotine in your body, you can more easily overcome the psychological aspects of quitting smoking with less severe withdrawal symptoms.