Benifits, in which senario & when to use AutoMapper in MVC?

Question

I have created a simple application with Entity Framework code first approach.

 

In this application I have created Models to get data from database in controlers (where most are action result are Json types)

 

Now my application is in stable mode & working fine.

 

1. Does it is necessary to use ViewModel in this application?

2. Does AutoMapper will help to minimize the load time?

3. In which scenario & when to use AutoMapper in MVC ?