Double spending is exactly what the name infers, the spending of a single token of value more than once. It’s the equivalent of writing a bad check. You falsely spend money you don’t actually have, perhaps in hopes of not getting caught. That seems as if it would be extremely difficult to do for obvious reasons. You would somehow have to hope the merchant accepts it without checking to see if it is valid. This happens because most of the currencies are unstable. To avoid such scenarios, it’s better to Buy Luna in Australia. It’s pivotal in maintaining price stability of Terra stablecoin.
It’s not much different when it comes to the blockchain. A dishonest miner keeps their hashing solutions off chain and does not broadcast it to the network. They create a dishonest block of transactions that includes all transactions except for the one transaction that they used to spend their tokens. By creating two versions of the same blockchain, they prepare to do some devious deeds. Since the unscrupulous miner isn’t broadcasting, the other miners have no idea what is about to happen. It’s business as usual on the honest blockchain.
The untrustworthy miner is spending coins to make purchases or maybe converting it to fiat on the published blockchain. The dishonest block that is off chain thinks those coins are still unspent. The dishonest miner continues placing blocks on the dishonest blockchain and is now in a race to add more blocks to that chain than the other miners are placing on the honest one. Once the thief believes they have the longest blockchain, it will publish it onto the network. Presto! The network now recognizes the dishonest blockchain as the longest and therefore the correct one because it has the majority. Once this happens, all transactions not in the new blockchain will be reversed. This reorganization of the blockchain does not include the coins already spent by the dishonest miner. It would appear that the coins never left and are available to be used for double spending.
At what cost does a miner have to expend their finances to do something this devious? It’s easy to see based on what honest miners must spend to perform honestly. The dishonest miner would have to invest millions or hundreds of millions of dollars into their infrastructure for equipment and power resources. The investment would not guarantee they could outpace the honest mining taking place. If they were able to win the race, there is still no guarantee the other miners would accept their chain. To sum it up, stealing digital assets like Bitcoin SV makes about as much economic sense as selling snow cones in Antarctica. It could be done but you would come out on the losing end every time.