We have added a new feature to List Selection and Multi Lookup fields: Lookup Filters. In both types of field you specify an app and form to lookup, and the field’s list shows the records that match the app and form. A Lookup Filter is an optional way to further refine what is shown in the displayed list, to those records where one or more fields on the record also match specified values.

> Detailed information on how to use Lookup Filers, from our Support site