A geodatabase is a central storage location for features, related datasets and behaviors.
They consist of the following components –
An organizational group of feature classes that share a common spatial reference.
A storage location for coordinates and feature attributes. Feature classes of the geometry type point, line or polygon. Attributes store inforamtion about these locations.
These are the questions you ask about a location (feature). Attribute fields are where attribute values are stored. They are properties of a feature class and are of the data type short integer, long integer, float, double, text, date, blob or guid. Attribute values are the possible answers to those questions
Domains are the range or set of possible answers or attribute values for a feature class. They are critical in enforcing data integrity. Domains are of the domain type range or coded value. Note, although domains are properties of the geodatabase, they do not appear in the ArcCatalog tree.