Narcotic drugs are substances that can relieve pain and induce sleep, often derived from opium or synthesized in laboratories. They work by affecting the brain's receptors, leading to feelings of euphoria but also potential addiction and dependence. Common examples include morphine and codeine. Psychotropic substances, on the other hand, alter mood, perception, and cognitive functions. These include a wide range of drugs, such as antidepressants, anxiolytics, and hallucinogens. While some are used therapeutically, others can lead to misuse and mental health issues, highlighting the importance of responsible use and regulation.