Drugs are substances that can alter the body's functions, often used for medical purposes to treat, prevent, or diagnose illnesses. They can be classified into various categories, including prescription medications, which require a doctor's approval, and over-the-counter drugs, which can be purchased without a prescription. However, not all drugs are used for health benefits. Some, like recreational drugs, are consumed for their psychoactive effects and can lead to addiction or health issues. Understanding the different types of drugs and their effects is crucial for making informed choices about their use.