Empathogenic NPS (or entactogens) are a class of drugs that produce experiences of emotional communion, oneness, relatedness, emotional openness. These NPS act like MDMA or ecstacy. These substance also have a stimulating effect and are therefore partly stimulants.
Examples are 4-FA, 5/6 APB and PMMA

Short term risk include mood swings, nausea, anxiousness, vomiting, overheating and risk of dehydration.
Long term risks include depression, dependancy. Not all long term effects are currently known

Empathogens are most commenly swallowed or snorted.

For more (fairly technical) information on the different NPS’s, you can visit these pages of the UN and Tripsit

Source: 1, 2, 3