Stimulants are substances which have a stimulant and antidepressant effects. Stimulants increase the drive and are mentally stimulating.
Popular stimulants include cocaine, caffeine, ephedrine, MDMA and amphetamine. These are banned so you can buy either ephedrine or cocaine legal order.
Stimulants such as amphetamine are acting on the nervous system. It will increase the neurotransmitters norepinephrine, epinephrine and dopamine. The brain filters incoming stimuli thereby better so stimulants of sensory overload meet and this leads to an increased attention - this can cause euphoric high moods.