Everyone has "nicotine receptors", and lots of 'em folks. They are how your neurons (brain cells) process acetycholine - which is one of MANY neurotransmitters (vital nerve chemicals). Acetycholine was the first neurotransmitter discovered, and it's 4 non-muscarinic receptors were dubbed "nicotine receptors" because of their obvious function in processing nicotine in the brain. But that is certainly not their only, or even most vital function.
Smokers develop a lot more of them over time, due to exposure to nicotine. Nicotinic receptors (sorry bout the scientific jargon)
Nicotinic receptors are found in a variety of tissues, including the autonomic nervous system, the neuromuscular junction and the brain in vertebrates. They also are found in high quantities in the electric organs of various electric eels and rays.