What is the difference between a stimulant and an amphetamine?

What is the difference between a stimulant and an amphetamine?
Stimulants are a group of substances that stimulate the body's central nervous system (CNS). It incorporates most legal and illegal sources which introduce chemicals into your body, typically characterized by their effects of speeding up the whole CNS.
Amphetamines are stimulants, but they are a certain specific type due to their distinct characteristics and attributes. Amphetamines do stimulate the CNS, but are much more powerful than say, caffeine. Amps (mainly dextroamphetamines) act on the dopaminergic and norepinephrinergic systems of the brain - increasing the levels of dopamine and norepinephrine. Amphetamines are controlled substances in the United States because of their higher potential for abuse. "On the streets", amphetamines are commonly referred to as "speed". (No, methamphetamine is not the true speed! - Common misconception...) Studies have also been done recently in attempts to further prove that amphetamines can possibly cause chemical dependency in the body.
A simple analogy:
Stimulant is to amphetamine, as tool is to hammer.
(General : specific, general : specific)
A hammer is a tool, but a tool is not always a hammer. Same with stimulants and amps. Amphetamines are stimulants, but not every stimulant is an amphetamine.
Hope this answers your question, mate :)
stimulants are a general class of drugs that include cocaine, caffeine and amphetamines.