What is the Partition Manager orig_span item in pm_static yml files?

The examples for the Matter Light Bulb app and others contain pm_static_...yml files with sections that look like:

mcuboot_primary:
  orig_span: &id001
  - mcuboot_pad
  - app
  span: *id001
  address: 0xD000
  region: flash_primary
  size: 0x165000

I cannot find "orig_span" in the Partition Manager documentation, nor anything about the "&id001" and "*id001" values. What are these and are they documented somewhere?

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