Domain is physical territory, almost always within a town or city, to which your character controls access for the purpose of feeding. She can't keep the living inhabitants from going about their business, but she can keep watch herself. She can also have allies or servants specifically look for unfamiliar vampires and alert her when they find some. Domain refers specifically to the land and properties on it, as opposed to the people who may dwell there (which is the emphasis of Herd). Domain plays an important part in Cainite society - vampires who lack significant domain seldom earn respect - but it isn't an automatic entitlement to status among Cainites.
Each level of Domain reduces the difficulty of feeding checks by one for your character and those whom the character allows in. It also adds to your starting (not maximum) blood pool. If you use the domain security option, each dot of domain security raises the difficulty of feeding checks by one for uninvited vampires.
• A family home or a farm and its outlying properties - enough for a basic haven.
•• A church or other large structure, a pier and adjacent warehouse or a bridge and a ford - some place with ready but easily controllable access to the outside world.
••• A city block or the buildings around a country crossroad - some place with more opportunities for concealment but less through security.
•••• A labyrinth, network of cisterns, the estates on a hill overlooking a town or the inns and watch posts on each side of a mountain pass - a place with both prospects and security.
••••• A ghetto district, self-sustaining border garrison or multi-family farm holding.
As noted previously, characters in a coterie can share their domain resources for better results. Six to eight dots secure of all of a small town as domain. Ten to 15 dots secure an important but not huge trading destination or center of pilgrimage. A city such as Rome (let alone Cairo or Baghdad) would require many hundreds of Domain points.