On a BIOS system with a single partition, the "System" label might actually be on the C: drive itself. But modern Windows usually separates boot files.
When you see , you are typically in the Windows Setup environment or a disk management tool. Here is the breakdown: drive 0 partition 1 system
You will see .
So = The first partition on your primary disk. System = This partition holds what’s needed to boot the OS. On a BIOS system with a single partition,