Database Role & Application

What is the basic difference between these roles..
I know as per books but how it can be used in real life. We have all roles
defined as database roles.. where we can use app roleDave,
here are some good articles:
http://www.databasejournal.com/feat...cle.php/3363521
http://www.sqlteam.com/item.asp?ItemID=864
http://vyaskn.tripod.com/sql_server...t_practices.htm
Dejan Sarka, SQL Server MVP
Associate Mentor
www.SolidQualityLearning.com
"Dave" <Dave@.discussions.microsoft.com> wrote in message
news:1D3ECF9A-E3C5-403A-8F26-96733B267561@.microsoft.com...
> What is the basic difference between these roles..
> I know as per books but how it can be used in real life. We have all roles
> defined as database roles.. where we can use app role