1. The Core Concept: The "God Mode" of Blockchains

To understand MEV, you first need to understand how a transaction works. When you trade on Ethereum, your transaction goes into a "waiting room" called the Mempool.

The people responsible for building the next block (formerly Miners, now Validators) pick transactions from this waiting room.

• The Power: Validators don't just pick transactions; they decide the exact order of them.
• The Profit: Because they control the order, they can insert their own transactions before or after yours to make a profit. This extra profit is called MEV.

Link to the next concept: How exactly does changing the order of transactions make money? Through specific Strategies.

2. The Strategies: The Sandwich Attack

MEV is essentially an invisible game played by bots. Here are the three main moves:

• Frontrunning: A bot sees you are about to buy a token (which will raise the price). The bot bribes the validator to let them buy it first at the cheap price.
• Backrunning: The bot sees a big trade happen that changes prices on an exchange. They immediately place a trade right after it to profit from the price difference (Arbitrage).
• The Sandwich Attack: This is the "toxic" combo.
  1. Alice tries to buy a token.
  2. Bot buys it before her (raising the price).
  3. Alice buys it at the inflated price.
  4. Bot sells it after her (locking in profit). Result: Alice gets fewer tokens than she expected, and the bot steals the value.

Link to the next concept: In the early days, this process was incredibly messy and expensive. This was the PGA Era.

3. The Past: Priority Gas Auctions (PGA)

Before organized tools existed, MEV bots fought in public.

• The War: Two bots would see a profit opportunity. To beat each other, they would keep increasing the gas fee (transaction fee) they were willing to pay.
• The Damage: This "bidding war" happened on the public network. It clogged up Ethereum, making fees expensive for normal users who weren't even playing the game.

Link to the next concept: To save the network from being clogged by these wars, a solution was created: Flashbots.

4. The Fix: Flashbots and Hidden Channels

A group called Flashbots created a way to move these bidding wars off the main road.