When Database created in ASP.NET CORE 1.1 code first in Visual Studio 2017

Hello guys,

I created ASP.NET CORE 1.1 code first Project in Visual Studio 2017,

I made my model classes and AppContext class for Database, but my Database created only when i made Migration,

But I thought that the Database is created when i run my application and every time i run application it created with any update i make in the model classes 

and any change i make to class model will reflect on the database, as example when add new property to specific class that add new column in the table in the database

But what about using application in Production level by end users ?

can any one explain what happen under the hood please