Link to Single Field from Multiple Tables
This data type is used to create a field that pulls its possible values from more than one source table. For example, you might have the Assigned To field in the Case table pull its values from the Contact table as well as from the Team table so you can assign not only to individuals but also to whole teams.
When you setup this field for the Case table by navigating to Setup > Tables > Edit > Fields tab, add Source tables one by one in the first tab of the Field wizard:
Once fields have been created, they will display the multiple links in the field list:
The drop-down field is often the best way to present such relationship when editing and creating the Case. Note that the Assigned To field accepts both Team and Full Name values.
The Case record will appear in the Case record.
It's possible to construct a field of this type using source fields that have different data types, such as a Text, Integer, and Floating Point fields. In such a case, the field is represented as a text field.