Drug – a substance that causes a physical or emotional change in a person. A drug is a substance that when put into the body can change the way the body works. This lecture briefly describe on introduction to drugs. Here also focus on effects of drugs, psychoactive effects and Drug Use, Drug Misuse, Drug abuse etc. Effect – the influence a drug has on the body and the mind or both. Drug Use – taking meds properly and in its correct dosage. Finally find out why do people use drugs: Curiosity, Peer pressure, Pleasure seeking, Act of rebellion and Boredom.