> Is the Inbox by Google application what was formerly the stock mail
> application called "Email"?

No, it is not. 

As said already in earlier Answer, the support for Stock Email app is no more. I recently bought **Moto G3** and it came pre-installed with Gmail **with no other Email app**.

[Inbox][1] is developed by Gmail team. Hence, all your messages from Gmail are with Inbox, along with the reliability and spam protection of Gmail.

But there are few **advantages** of Inbox over Gmail App.

- **Creating a new labels**: If you want to [create new labels][2] using Gmail app, it is not supported, Yet in Android. However, you can create new label using Inbox app.
- **Inserting Images inline**: Attaching inline images is not supported by Gmail, but you can attach images inline in the Inbox by Gmail app for Android.

But on **flip** side, Inbox does not support App widgets like Gmail app do.



  


  [1]: https://play.google.com/store/apps/details?id=com.google.android.apps.inbox
  [2]: https://android.stackexchange.com/questions/96253/create-new-labels-in-gmail-app