There are various different strains of fungus that produce various kinds of mushrooms - they all contain Psilocybin as their chief psychoactive substance.
This page contains a listing of all known 'shrooms:
http://www.erowid.org/plants/mushrooms/mushrooms_info12.shtml
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'shrooms tend to have several different types of trips from my research:
Sometimes it's a little like an all-night drunkeness.
For other times it can feel euphoric, similar to MDMA and other ecstacy, in the sense that it becomes very *emotional*, and phyisical surroundings take on their own sensitivity.
Then, of course, there's the balls-out hallucinogenic trip - open-eye visuals, a physical sickness that can flip to an epiphany of revalation that makes only little sense the next day, etc.
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As with many drugs that are around today, 'shrooms are much more potent, though can be a little less pure, and much more expensive than they were in the 1960's. Possibly this leads to different psychoactive experiences ...
As always, do the research and know your supplier.