Frontrunning places a transaction before yours; backrunning places one immediately after. Both exploit ordering for profit beyond sandwich attacks on DEXs.
Searchers bundle buy-low and sell-high across DEXs in one transaction — reverting if unprofitable. No inventory risk; pure math. Competitive and low-margin except during volatility.
Understanding both patterns helps you see why some MEV is tolerated as market plumbing while frontrunning retail trades is treated as extraction.