The demarcation between religion and cults is a fuzzy line. Religion vs. cults is a false dichotomy,
like science vs. pseudoscience, where there is
a spectrum between the two. Cults have one or more of the folowing features:
Disconnect from non-member family and friends
Cults can need to prevent outside influences from affecting recruits and members, and assert that outsiders are the source of members' problems and the cult is the solution. Isolation is a form of information control.
Cults can be intolerant, judgmental or punative of inquiry, not only to outsiders but also to members. Mostly just scripted information is available.
Hostility towards critics, especially ex-members
Cults can threaten critics with physical harm, lawsuits, black lists and other intimidation techniques. Confidential information divulged during recruitment and membership can be used against those former members. Members may be required to disconnect from ex-members, even family ex-members.
Cults can make members feel obligated to spend increasing time and/or money. Keeping members busy is also a form of information control and indoctrination.
Simple solutions to complex problems
Cults can promise answers to all your problems, or they promise a better afterlife, and can claim to be "in the know" while the rest of society are misguided sheep.
Cults can feign affection or friendship with overwhelming positive attention in a deliberate attempt to recruit, convert or influence the inductee.
Self-contained belief system
Cults can have a circular non-falsifiable belief system.
Cults can have a power structure of unquestionable authority.