Help understanding snapshot vs backup

I'm pretty new to using btrfs and just installed btrbk. I was wondering if someone could help explain some of the dynamics to me. I have two btrfs arrays: data_array and backup_array. I have set up btrbk to make snapshots of a subvolume in the mnt/data_array/mydata These are stored on the data_array. Is it correct that they take up very little space but simply reference the blocks of data on the data_array? So if data becomes corrupted on data_array it's similarly corrupted on those snapshots?

Then I also have btrbk sending backups to a separate set of drives in the backup_array onto a subvolume mnt/backup_array/backups The first one took 1.5 hours to transfer but each one after that has only taken seconds. I'm trying to understand how it's all tied together. Is the first transfer a complete copy of the original data files? And then are the subsequent snapshots referencing that first transfer that is on the backup subvolume? I'm guessing that is the case but wasn't sure. In this respect if I experience complete loss of my data_array then I can still restore off the backup_array? However, if that first large snapshot that was transferred over to the backup_array gets corrupted then all my other backups are gone as well? Are those the incremental backups? And do I need to somehow be setting up full backups?

Thanks for any help in explaining this to me.

No source file, test, or entry point is named. Start by reviewing btrbk's snapshot and backup behavior documentation, then ensure the explanation covers local snapshots, transfers to backup_array, incremental backups, corruption implications, and whether full backups are needed.

Written by the indexing model from the issue text.