The first line, which has been rendered obsolete by the BCD (Boot Configuration Data store) in Windows Vista, Windows 7, and Server 2008, is from a boot.ini file for Windows XP or Server 2003, and is located in the root directory of the system drive. That tells Windows where to go (what disk and partition) to find the system files it needs to boot.
Look here for a detailed explanation of "multi" and "rdisk". The rest means that look at disk 0 (they start at 0 and move up from there, and you can see their numbers in the disk manager), partition 1 (unlike the disks, these start being numbered at 1 and go up).
As far as the enumeration of devices goes, it is a very complicated programming subject, which is explained here if you want your head to explode. The format you gave is how the device is addressed as a hardware ID in the registry.
As a practical matter you can look at this registry key
to match any error you may get to a "hardware ID" value in one of the sub keys to determine exactly what device the error may refer to.