There are 6 basic types of domains.
SYNONYM Domain is a reserved domain. You can add values to this type of domain but you cannot add or delete it.
ALN Domain is a alphanumeric value domain.
NUMERIC is a numeric value domain.
NUMRANGE is a specified range of values in a domain.
TABLE is a dynamic set of values derived from an object attribute in a domain.
CROSSOVER is a particular value that is pulled from another record.