Zones In SharePoint

Zones are of Five types:

Internet
Intranet
Extranet
Custom
Default

These five are not different from each other. They use the same Web Application and same content, which is stored in the Application with the same database.

What is the difference?

The main difference is each zone carries its own IIS Website after extending it from SharePoint. These zones have their own URLs configured for them.
These zones have their own Port number, Protocol (http or https).
Different authentication methods can be used to login in the different zones.
E.g:- Forms authentication in Intranet, default Windows authentication etc.
You configure your Blob and Distributed cache differently for the different zones.

For example

Let’s say you have a building, which is your Web Application with a default zone, as its main entrance with its own authentication Service like Windows authentication in the front for SharePoint administrators and adding other zones is like adding a few other entrances to your Web Application with Facebook as the identity provider for your federated partners.

Extending your Web Application

Go to Central Administration- Application Management-Manage Web Application -Select the Web Application -Go to Ribbon - Extend.
In the Create a new IIS website section, give the Web Application a name.
Give the required port.
If you have https enabled, select Yes in Use Secure Socket Layer section.
In the next section, choose your type of authentication, which you want to use for this zone.
Now, click on save.

Adding Extranet Users in SharePoint

Open Central Administration site - Application Management - [under Application Security] Policy for Web Application - Add Users-Zone: Extranet-NEXT-Type User Name [click on the icon below it to check]-Permission: Full Control-Finish.

Repeat the same to add all the target users.

We have created an extranet site, added the users and enabled the form authentication. We can now open the site http://spdemoserver:20001/ .

We found a login page, which is opened. Once we login with the user credentials, which we created, we will be able to access the extended site.