Visual Studio will automatically create a database when you create a new ASP.NET Core Web App project using Visual Studio and select a default authentication type for individual accounts. Once the database is created, it may be a little challenging to find. Where is it located on your windows computer?
The localdb file is in your Windows computer's C:\Users\{MyUser}\ folder.
It will have a naming convention of asp.net-{YourProjectName}-somelongcrypticid.
For the Demo Project created in the DemoProject tutorial (here), the database file name is aspnet-DemoProject-9BF863CD-3CEB-4FA4-B29B-4EF09A581CD7.
Recommendations
Instead of using the Entity Framework generated database file, it is best to install Microsoft SQL Server and use Microsoft SQL Server Management Studio to create and manage your databases. Why?
The database file created by Entity Framework is primarily for individuals who aren't concerned about the underlying database tables or where the data is stored. However, if you are a full-stack developer, you want direct access and complete control over the database.
Once you have downloaded and installed Microsoft SQL Server and created your database, update the applications connection string in the appsettings.json file in your ASP.NET Core MVC project.
After updating the connection string, use Package Manager Console and Entity Framework’s migration feature to update the new database with the default tables.