SharePoint Alternate Access Mapping (AAM)

Alternate Access Mapping: This Mapping between internal and public URLs in SharePoint :

  The Main differentiation between internal and  public URLs :

   Internal refers to the URL of a web request as it is received by SharePoint 2013.

  Public refers to the URL by which SharePoint will format links that correspond to    

   requests that match one of the internal URLs on that zone when it returns a response

[Important]Common mistake:

Creating a new AAM zone without extending the Web Application or manually altering the Public URL
of any zone from Central Admin. This can cause ambiguous scenarios for routing requests to
SharePoint and result in connectivity issues.