Amphetamine-type stimulants (Amphetamines) are a group of drugs commonly known as speed. They are classed as stimulant drugs. This means that they affect the central nervous system by speeding up the activity of certain chemicals in the brain, producing a feeling of increased alertness and reduced fatigue.http://drugaware.com.au/getting-the-facts/drug-types/amphetamines/#What-are-Amphetamines-