Substance abuse refers to the harmful or hazardous use of psychoactive substances, including alcohol and illicit drugs. The document discusses the definition of substance abuse and addiction, common substances of abuse like alcohol, tobacco and cocaine, short-term and long-term effects of substance use, and reasons why students may fall victim to substance abuse, including curiosity, peer pressure, and mental health issues. It provides information on identifying signs of intoxication and emphasizes the importance of making healthy choices to avoid the negative consequences of substance abuse.