Application ID

I want to develop an app on Unity, and it requires an Application ID

Now I don't have one, but it seems I need to fill out a store application with a pitch and all to get one

Thing is, I'm doing this to PRACTICE my coding, not so much to PUBLISH right away, I'm an amateur on a good day, and just plain inexperienced every other day

Do I NEED the Application ID, and if so, am I going about this wrong, or is the ID for Publishing purposes only