Currently, I am a little bit confuse related to Alternate Access Mapping. Could you please clear me about this "Extend the Web Application and Alternate Access Mapping is the same thing in SharePoint 2013"?
they are different things:
Extended Web Application: If you want to expose the same content in a Web application to different types of users by using additional URLs or authentication methods, you can extend an existing Web application into a new zone. When you extend the Web application into a new zone, you create a separate Internet Information Services (IIS) Web site to serve the same content, but with a unique URL and authentication type.
Adding the Entry the AAM is, simply access the Same site with Different URLs only. You will not get different authentication or other benifits. i.e web app http://abc and you create another url for that web app http://efg.
No, Both are different concepts like East-West.
If we talk about Alternate Access Mapping then its the same Web Application having more than one access URL, the URLs are Internal URL and Public URL. When you manage AAM then in that case you are just creating different URL which will be pointing towards the same Web Application in SharePoint and is equivalent to creating multiple HTTP bindings in IIS for a single Web Application. Additionally we cannot have different authentication mechanism if we are using AAM
While when you use "Extended Web Application" mechanism, then it create a different Web Application in SharePoint as well as in IIS. And you can have different authentication mechanism for both. Internally both the Web Application will share the common Content Database hence the content displayed in both the Web Application will be similar and changes in one Web Application will directly affect the other and content will be displayed in both the Web Application.
The above mentioned points are very few of the explanations. If you need to go in detail then you can go through SharePoint Alternate Access Mapping (AAM) for Dummies and Understanding Extended Web Application SharePoint
Let me know you need more assist on this.