Cults fascinate us. That's one reason why there is very little challenge to filling the seats of a college class on the subject of cults. Any YouTube video on cults will get thousands of hits almost effortlessly.
We want to know what it is that makes them what they are. We want to know what makes them different. We want to know what makes them dangerous.
The word "cult" means something different to different people. Thoughts of David Koresh, and the Branch Davidians come to mind. Or maybe you think of Jim Jones and the horrible massacre that happened in Jonestown. This is where we get the no common idiom, "He drank the Kool-Aid".
And who can forget Heaven's Gate in California? Those people believed that the aliens were coming in they committed suicide I don't think there's any question that cults can be extremely dangerous.
Taking all of this into consideration, we have a very broad brush to paint for us what a cult is. But to be honest, the idea of what constitutes a cult is broader than any of these.