This document discusses different types of drugs including stimulants like caffeine, amphetamines, and cocaine that increase nervous system activity. It also discusses depressants like alcohol, opioids, and solvents that decrease nervous system activity. Hallucinogens like LSD and cannabis are described as altering perception. The document provides details on the effects of each drug type and warns that long-term drug use can damage the body and brain, lead to dependence and addiction, and have social consequences.