They are a group of quite variable synthetic drugs. They share some similarity to both amphetamine and to cannabis. They are very debilitating. It is unlikely someone could be under the influence of them and seem normal. There have been a few deaths associated with them due to the stress they put on the cardiovascular system. They are being made illegal, but because they are novel chemicals, the ability to test for them is developing. Basically, they are legal until they are caught.