The concept of system partitioning and boot partitioning should be clearly defined by friends who often reconnect, but for beginners it can be a lot of effort to distinguish between these two concepts. Let me explain to you here.
From the Microsoft Help document, see:
System partitions are partitions that contain the hardware-specific files required to load Windows (such as Bootmgr), and the system partition can (not be) the same as the boot partition.
A boot partition refers to a partition that contains the Windows operating system and its supporting files.
In the case of traditional WinXP + Win7, for Win7, its system partition is the first partition (because the specific files required to load windows are in the partition), and the boot partition is the second partition (because the Windows operating system directory is on that partition). Here the system partition, the boot partition is combined, indicating that this partition contains system files and boot files, it can be explained that the system is autonomous, independent start-up.