There's an old idea called "front running". Back when the stock market was based on pieces of paper being passed around, you could hear something useful/valuable and literally outrun the other person to make a profitable trade.

To understand the equivalent in Ethereum you need to understand 3 things: 1. All transactions require something called "gas" which is based on the complexity of the transaction. The simplest transfer is 21,000 and seriously complicated tasks can go up to millions (11 million-ish is the cap now) 2. Miner's get to decide which transactions go in the blocks they mine. They get the fees associated with those transactions, so they pick the most profitable. 3. You don't get to decide how much gas your transaction uses, but you do get to decide how much Ether you're willing to spend per unit of gas, e.g. gasPrice of 3 Gwei(1/1,000,000,000 of an Ether) means you multiply your 21,000 gas transaction by .000000003 and that's how much Ether the miner gets for including your transaction.

Net Result: Right now on Ethereum Mainnet 100 Gwei is standard, so I see you have a transaction waiting where you offered 100 Gwei. I just swap out my address instead of yours and offer 200 Gwei. Now a miner will pick up my transaction first because they get twice the profits for the exact same amount of work.

“Mempool” is a pool of transactions and price offered for each VM instruction rather than a queue.

Frontrunning in this context is detecting transactions that yield in profit and submitting them to the pool with a higher price for each instruction (gas price).

The queue is not a "first come first serve" queue but a "highest paying customers first" queue.

This is the bit I didn't get about the article. How could the original owner of the $12K get their money out without getting pwned by the same bots?