Windows DVD file library question?

On the Windows DVD there are a bunch of files. Among them is a file called "bootmgr". The problem I'm having is figuring out the extension of this file. I went and changed some properties so that Windows displays all file extensions but it's still not showing one for this file. I understand it's a boot manager of some sort but it just doesn't make sense, not to have a file extension if it is a file. Under that file is another boot manager but it has a file extension, it's called "bootmgr.efi", and I know what it does and why it's there. It's the other, unknown boot manager, that's bothering me as I don't know what it does and what kind of file it is? Does anyone know the answer to that?