Lookup field
A field in a custom object designated to store values that
are used as the names of the object’s records. These names display
on editor tabs and the navigation pane’s Recent Items list. For instance,
the Recent Items list displays incident reference numbers since the
Reference # field is designated as the lookup field for incidents.
Values in lookup fields are also displayed in reports instead of the
ID values from fields in other tables that link to the lookup field’s
table. For instance, while the incidents table’s Assigned Account field stores account ID numbers, the values
displayed for this field in reports are from the accounts table’s Full Name field.