Usually, you split your database when you need to completely remove some persons or families from the database, you need to make a copy of those persons or families to move data to another database, or you need to send them to other researchers.
Before you run this tool, you must select a person you want to copy in the person list on "Individuals" tab. Then you use one of four available methods in this tool: pick out all relations, pick out ancestors only, pick out descendants only, or family only. When all persons have been picked out, you can save them as a separate database file, or remove them all from the current database. You can combine these operationsthat is, save the picked results to a database first, and then remove it from the current database with the "Delete" button.
There are two lists displayed when using this tool: the list on the left contains all the picked persons, and the list on the right contains persons that were not picked by the tool.