Please explain RB5009 storage

I would like to understand the disk1 or disk2 mounts.

I understand the RB5009 has 1GB of nand storage.

How do I access that?

When I create mounts in a container and name them disk1 or disk2, are these just folders in that nand storage?

I’ve looked at /system/disks and /files, but I don’t see anything that would show me how disk1 is created or used.

Everything I have found online says these disks are names of external storage cards.

Thank you.