Trying to Understand 'Blockchain Currency' ... maybe my brain's rejecting it like bad food ...

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I mean, I guess I understand the basic concept of the decentralized verification ledger (tho my understanding probably isn't "the one they're using"): something like 'ALL the currency-users keep a ledger, and verify transactions between pairs of fellow currency-users.' But my brain 'bails out' at the "miners"---I read (scrolling WAY DOWN at the link) that the transactions are verified 'when a majority of the "miners" (computers trying to decrypt the block) guess the same number'? 'bailing out' with a "What on Earth has 'guessing the right number' got to do with "a valid transaction"?' https://cryptocurrencyfacts.com/how-does-cryptocurrency-work-for-beginners/ I suppose it might go back to the way currency ORIGINALLY worked with 'miners' (the REAL ones, digging in the ground to find a precious metal)---a miner would bring his precious metal to a bank, the banker would store it in his safe and in return issue the miner a Promissory Note (or a few) good for the value of the metal stored, and the miner could then trade those Notes (rather than lugging around the whole treasury) for goods-&-services. ... I'm a visual learner, so the diagram starts at explaining it. Maybe you know how it works---who decides what math-problem wins the block, etc....