In reality, cults only care about making money or gaining political power for their leaders, and have no remorse about exploiting and intimidating their members in the process. Cults are basically like evil corporations, only much, much eviler and dangerous.
To understand the psychology of a cult member, first:
1. Picture some uneducated, unmarried middle-aged loser who works 50 hours a week at Wal-Mart for 8 bucks an hour, and tells everyone how much he loves his job and how nice his bosses are, and is willing to rat you out if he hears you say anything negative about your job. Creepy right?
2. Now, picture a person who is the equivalent of the guy above, but does the same work for FREE, or worse yet, even PAYS out of his OWN POCKET for the "privilege" of doing work for his organization (aka his cult).
This is the psychology of a cult member - they are literally the lowest common denominator of society. Essentially, they are the "teacher's pet" kid who annoyed the hell out of everyone in 3rd grade, and never outgrew this psychology even in adulthood. Avoid cult members at all costs, they are at best, delusional, and at worst, downright sociopaths.
Some have members practice certain rituals or follow a set of principle rules. The group usually believes its way is the only correct way to live life, and all non-members are doomed to some horrible fate if they cannot be persuaded to join.
Members are often recruited or by some means persuaded to join, rarely if ever knowing how destructive and harmful a cult can be -- rarely knowing that it IS a cult. Though they usual come off as being generous, caring and in the best interests of their members, cults are inherently based on furthering the desires of cult leaders.
Cult leaders commonly use thought reform or "brainwashing", in conjunction with other methods, to slowly and deliberately reel in more control of said members. In many cases, members may eventually forsake their friends and family (non-members are viewed as "wrong" or "bad") and give up their careers, homes and/or money to the leader.
Note: Not all cults are harmful in nature. Many are benign, i.e. trekkies.
See www.rickross.com for more extensive definitions.
2. A small or unconventional religion