Select Display Criteria - "Latest Items"

[ABBA GRAPHICS]

Hello, created a custome app for announcements and would like to know when placing the module on a page what does the "Latest Items" under display criteria actually do?

How does it work out what the latest items are?

Are announcements submitted displayed on the daily, weekly or monthly?

How do you or can you set the display time?

Are announcements older then a week removed automatically?

really appreciate your help... thanks