What are Magic Mushrooms?

Psilocybin mushrooms are fungi that contain psychoactive indole alkaloids. 
There are multiple colloquial terms for psilocybin mushrooms, the most common being shrooms and magic mushrooms. 
Biological genera containing psilocybin mushrooms include Agrocybe, Conocybe, Copelandia, Galerina, Gerronema, Gymnopilus, Hypholoma, Inocybe, Mycena, Panaeolus, Pluteus, and Psilocybe. 
There are approximately 190 species of psilocybin mushrooms and most of them fall in the genus Psilocybe.
Psilocybin mushrooms have likely been used since prehistoric times and may have been depicted in rock art. Many cultures have used these mushrooms in religious rites. 
In modern Western society they are used recreationally for their psychedelic effects. 
Recent studies done at Imperial College London and Johns Hopkins School of Medicine conclude that when used properly, psilocybin acts as an anti-depressant as suggested by fMRI brain scans.
(Source: Wiki)