Speed is the generalized term for amphetamines. Amphetamine classifies the chemical Amphetamine but also any chemical that is similar in chemical buildup to an Amphetamine, which include, but are not limited to: Acetedron, Allodene, Adipan, Sympatedrine, Psychedrine, Isomyn, Isoamyne, Mecodrin, Norephadrane, Novydrine, Elastonon, Ortedrine, Phenedrine, Profamina, Propisamine, Sympamine, and Simpatedrin.

Methamphetamine in powder form is a hygroscopic, hydrochloride salt structure of the amphetamines. Methamphetamine is the active chemical in the drug Desoxyn, which is used to treat ADD and ADHD.

Speed is what its name implies, it speeds things up. It's just a stimulant, a strong one at that. Fight or flight adrenaline, yadda yadda yadda.

Someone might wanna go ahead and correct some of those amphetamine names, I typed them by hand so I may have incorrectly spelled a few.