Value that can be captured by choosing which transactions go into a block and in what order.
Why it matters
Ordering is a privilege, and it is worth money. Most MEV is unremarkable arbitrage, but the same privilege enables sandwiching a trade or racing a liquidation, and it means a pending transaction is public information before it settles.
What you can check
Slippage limits bound what an unfavourable ordering can cost on a trade. Private transaction routes change who sees a transaction before inclusion. Both are properties of how a transaction is submitted rather than of the protocol being used.
Not advice. Definitions are for understanding, not instruction. Nothing here is financial, legal, tax or security advice.