Apart from a secret cult, what exactly is the difference between a cult and a religion?

Its a complicated relation. A cult can be a religion and a religion can be a cult. Its all a matter of how they carry things out and their intentions. Usually something cult like uses information control or have beliefs that are very harmful to the members because they directly effect their daily life. An example of a cult like religion would be Jehovas Witness. Its usually sects and specific churches that act as cults rather than entire religions themselves.