If it is the program that I think it is, it allows the user to select an
operating
system to boot. If your PC only has Windows boot manager is not some
thing that you'll see when turn on your PC, but if you have multiple OSes
installed, the boot manager will display a list of detected OSes and let you
select the one you want to boot from.
An extension is the Advanced Boot Manager. This component is called
when you press F8 (usually repeatedly like a maniac) after the BIOS
information screen clears and befoe the Windows logo comes on. This
screen also displays a menu and allows you to select various versions
of Safe Mode and Last Known Good Configuration, among others.
Ifthis file/program is in your recovery partition it might be because it
is a copy that is used when using the recovery functionality, although
it could also be some other reason. HTH Saga