Stimulants are drugs that stimulate the brain and central nervous system, speeding up communication between the both. They usually increase alertness and physical activity. They include amphetamines, cocaine, crack and some inhalants like amyl or butyl nitrites. Your everyday coffee is a stimulant that many people have formed an addiction to. Those who stop drinking coffee even suffer withdrawal symptoms.
Depressants slow down the activity of the brain and nervous system, slowing down the communication between the two. For medical purposes they can calm nerves, relax muscles and useful for sleeping disorders such as insomnia. more on depressants >>
Hallucinogens interfere with the brain and central nervous system in a way that results in radical distortions of a user’s perception of reality. Profound images, sounds and sensations will be experienced, but they will not actually exist. These are vivid hallucinations