Everything about all the ledgers and the difference between transaction speed versus settlement speed you can read about in "Broken Money" by @LynAlden. It is also the first printed book I have read mentioning Nostr. 

https://image.nostr.build/293e4453f0b557835046662a721c1fa0c31ece0a0d5d5ad6436b0c2390644479.jpg