Password Policy Option "Allow Changes" setting

What does the Password Policy Option ‘Allow Changes’ setting on the Password tab do?

This setting is the amount of time before you can change your password again, once you have changed it (or initially set it).

It can be easily confused with the Expiration setting, but this one forces you to keep the password you have for however many days you have specified. If you have it set for 1 day(s), it means that they won’t be able to change their password for one day.  They have to keep their password at least one day.