Should I postfix application.yml?

My project structure (Spring / maven):

src / main / resources / application.yml src / test / resources / application.yml 

This is working well (when I launch test, it takes the test application.yml).

But often, I see posts where the application.yml is postfix to take the active profile: i.e.: application-test.yml for test profile.

What is the best practice here ? What is the point of postfixing the name ? When is it useful exactly ?