A Domain is a dimension that can be entered via astral projection that is owned by a Domain Keeper. Domains attract spirits and cause portals to open up randomly whenever the Domain is entered. Regular Domains lack rules and High Controllers. A common form of Regular Domain is a Mental Realm, however, not all Mental Realms are Regular Domains.
Mental Realms are Domains that exist within the mind. Everyone has a mental realm. They can be entered via astral projection and can be owned by a Domain Keeper of High Controller depending on the person. Mental Realms attract spirits and cause portals to open up randomly whenever they are entered.
A Controlled Domain that can be entered via astral projection and is controlled by a High Controller. Controlled Domains have rules that must be followed by everyone including the High Controller. The High Controller can make and change the rules as the High Controller pleases. Controlled Domains attract spirits and cuase portals to open up randomly whenever the Domain is entered.