The meaning of the Roles in SQL Server 2008 R2 Just because I’m confused around this issue I’d like to ask the following questions, and please I would like to receive clear and easy understandable answers. Not deep analyze.

1.What is the Roles for a programmer?
2.What is the role of the Schemas owned by this… which related with them?
3.What is the meaning and the use for Securables in Roles 
4.Why we add Users to a Role?
5.How we may handle the Roles in conjunction with to the Users, inside of a project? 

Thank you very much in advance.

ADDITIONAL INFORMATION

The reason uploading this question based on an issue which I’m facing developing a web.site. And the Issue is.
I have a number (100) of Web.Pages and a number (20.000) of Users (application users), each User has a special code, thus numerous Users belong to a Group (regarding to there code) and others in another Group.
Now, when a User of a certain Group tries to open a page I need a rule to look if he has the right to open this page.
For that reason I was thinking to use the Roles… But I steel don’t know if that is a good idea rather to create my own rule between Web.Pages and Application Users…
Roles are predefined sets of permissions on the database or on the server, that can be granted to the user as a package. Best practice is creating your own set of roles for the database, with the exact permissions that they need.