default zone in SharePoint
Zones are different logical paths expressed as URLs that allow access to the same web application. The default zones in sharepoint is 5. A web application can support up to five Default Zones. The available zone names are Default, Extranet, Intranet, Internet, and Custom.
One particular zone name can be used per web application. Zones using the same name across different web applications typically are available for the same user pool to control access for that group. For instance, your internal employees can use the Intranet zone to access all of the SharePoint sites configured to use that zone, giving that group the same sort of access to all relevant web applications. Each zone is expressed as a separate website in IIS. Zones isolate users based on authentication type, network zone, and policy. All zones have own Port number and Protocol http/https. Different authentication methods can be applied to login different zones like Forms authentication in Intranet and default Windows authentication. we can configure Blob and Distributed cache differently for different zones. When planning for zone deployment, particular attention must be paid to the Default zone, since access to this zone may be gained by anyone who is able to use a link to this zone, such as a URL sent via an automated administrative email. The Default one or any zone used for an outward-facing site must possess a high level of security.