I used to think Bitcoins were a computer file. Like if I had 1 BTC it would be a file on a hard drive that I could send someone. I had no idea about sats or blockchains back then. No wonder I was super confused. Probably got this idea from the news showing people looking through garbage dumps trying to find old hard drives that had their Bitcoin on them.
Discussion
I used to think there were physical bitcoins lol 
I used to think BTC are really stored inside a hardware wallet 😂
Before seeds you did have to backup your .dat file with all your private/public key pairs.
Then Im even more confused! I rather have the file I think! 🤔
How would they spend their BTC though? They would need to import it into a wallet? Kinda glad I came later, much less confusing now. 🤙
Yeah you have to load the file into your bitcoin core and rescan the blockchain for funds. The file was literally a list of all your private keys. More info here: https://en.bitcoin.it/wiki/Wallet