Create Database - Specify Difference Between 3 Name

Just wondering what the difference between the 3 name we specify are when creating a database e.g.

Code:
create database test_db on primary
(
name = 'test_db_dat',
filename = '......... est_db_dat.mdf'
....
)

So there are 3 example above in red where we specify the database name. From my understanding the first name we specify 'test_db' is for the benefit of SQL Server Management Studio Object Explorer. The second 'test_db_dat' is what i am confused about and the third '......... est_db_dat.mdf' is the physical file location and name.