Ghouls are created when a vampire feeds vitae to a living creature. Mechanically, this vitae is treated as a single point - for one lunar month, the ghoul has a point of vampiric blood in his system and acquires all the benefits (and drawbacks) of ghouling. Ghouls can hold multiple blood points in their system, but if they try to hold more than a human capacity, it has unpleasant side effects until the vitae replaces their normal blood. As long as a ghoul has vitae in his system, he remains a ghoul: vitae is lost at the rate of one point per month, and when used to power Disciplines. While a ghoul has blood in his system, he will not age.
Ghouls can learn vampiric Disciplines, but at a much slower rate than vampires. In addition, the maximum level learnable by a ghoul is a function of their domitor's Generation. Most ghouls cannot learn more than the first or second level of a Discipline. However, ghouls automatically get a dot of Potence for free.
Animals can also be ghouled, a tactic particularly favored by the Nosferatu. Animal ghouls tend to grow larger and mutate, the result being a somewhat horrifying parody of the original creature. In addition, almost all ghouled animals develop a taste for blood, regardless of their original diets.
Enough of the benefits, now the drawbacks. Ghouls are prone to frenzy, although not as strongly as a vampire. In addition, they are addicted to vitae - apart from the deleterious effects of the blood bond, Ghouls are subject to horrible side effects when the supply dries up. Without vitae, a ghoul will rapidly age physically to his actual chronological age, and ghouls over a century will crumble to dust quickly.
Ghouls are addicted to blood, and the control of blood is the primary way that ghouls are managed by their domitors — in addition to more traditional techniques like Dominate. The nastiest part of being a ghoul, of course, is that one is a slave to an inhuman monster that treats humans as chesspieces or the occasional light snack.
Various clans have different needs (and consequently treatment) for ghouls. The Ventrue make extensive use of ghouls, many of whom are only marginally aware of this fact. The Tzimisce are also fond of ghouls, although they tend to use them as one might use modeling clay, and such ghouls are almost invariably deformed. Tzimisce ghouls used as bodyguards or shock troops are called szlachta; others are combined into the gigantic, gestalt war ghouls called vozhd. Some unlucky ghouls are even shaped into architecture for Tzimisce havens.
Ghouls tend to fall into three major factions: Vassals, who are the stereotypical blood-addicted servant of a vampire; independent ghouls, who eke out an existence trading favors for blood, and revenants, the hereditary ghoul families. Largely associated with the Tzimisce, revenants actually manufacture their own weak vitae. If they weren't all insane cannibalistic freaks, they might even be a new form of humanity. There also exists a fourth faction composed of roving gangs of independent ghouls who hunt down vampires. They don't hunt the vampires for altruistic reasons or for revenge. They hunt vampires for two reasons: to get their fix of vitae, or because they think it's fun.