A lookup field lets you add information to a field from a list of values. There are two ways that a lookup field can get its list of values:
From a Lookup List: A list of values in a table or query. For example, instead of entering a CustomerID number, you could select it from a list of customers.
From a Value List: A list of values or options that you enter yourself. For example, you could add the values “FedEx,” “UPS,” and “AirBorne” to a Shipping field.
You can select to Allow Multiple Values. If you select this box, Access allows you to select multiple values from your list and store them in a single field (a multi-value field) For example, if a single product is made in two different countries, you can display both countries.