When working with a relational database such as access your tables will consist of Entities and Attributes. The fields or columns within the table describe characteristics or properties of an entity class. For example say you have a DISTRIBUTOR table the attributes within the table would consist of DISTRIBUTOR ID, DISTRIBUTOR NAME, DISTRIBUTOR PHONE NUMBER. An Attribute can be a Primary key such as DISTRIBUTOR ID or it can be a Foreign Key and be located in your ORDER table.
Within a database there are Domains which are rules applied to attributes in the database that must be followed. For example if you have an attribute such as DISTRIBUTOR PHONE NUMBER with an "integer domain" an entry of a character such as "XYZ" will not fit the domain only numbers. There are also 2 main constraints which are Referential Integrity and Entity Integrity. These Constraints set further restrictions upon the domains of the attributes such as only numbers 0-9 will be a sufficient entry in the DISTRIBUTOR PHONE NUMBER Attribute or perhaps a non-negative number can only be entered.