Why does mdadm output the opposite disk information?

Question

RAID

There is a working serviceable raid

Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb1[0] sdc1[1]
      7813893440 blocks super 1.2 [2/2] [UU]
      bitmap: 0/59 pages [0KB], 65536KB chunk

Obtaining information on a single disk gives a dual output:

mdadm -Q /dev/sdb1
/dev/sdb1: is not an md array
/dev/sdb1: device 0 in 2 device active raid1 /dev/md0.  Use mdadm --examine for more detail.

Answer 1

Why dual?
sdb1 is an array? No, it's not an array. is not an md array Array
volume - yes. device 0 in 2 device active raid1 /dev/md0

-Q, --query
Examine a device to see (1) if it is an md device and (2) if it
is a component of an md array. Information about what is
covered is presented.