In the chemical classifiacation also known as ‘cathinones, while some of them are known as ‘bath salts’. A stimulant substance (or ‘upper’) which temporarily increases alertness and energy. Physically they increase synaptic levels of serotonin, dopamine, and/or noradrenaline to produce a sense of euphoria and wellbeing; a “high”. “Bath salts” are central nervous system stimulants that inhibit the norepinephrine-dopamine reuptake system. These NPS act like amphetamine, cocaine.
Examples are Mephedrone, Methylone and alpha-PVP.

Short term risks include agitation, hyperthermia, seisures, delirium, stroke.
Long term risks include; depression, dependency, cognitive impairment, psychosis. Not all long term effect are currently known.

Stimulants are commonly swallowd (‘bombing’) or snorted. Less commonly injected (‘slamming’)

For more (fairly technical) information on the different stimulants, you can visit this Wikipedia page. Be aware though, that this page is not scientifically checked.

Source: 1, 2, 3