Bots do the work that keeps a dex price near the cex price. When a swap moves a pool, an arbitrageur trades it back within blocks, taking the difference. That profit is paid mostly by liquidity providers and is the ongoing cost behind impermanent-loss.
The business is infrastructure, not insight. Edges last milliseconds, so competitors fight over node latency, private order flow, flash-loan capital and block-builder relationships. Retail attempts to compete on public RPC endpoints reliably lose money to gas on failed attempts.
Understanding them is still useful for a discretionary trader: it explains why obvious cross-venue gaps close before you can click, why a token with no arbitrageurs stays mispriced, and why funding and basis levels across venues converge without anyone announcing it.
Related: mev, flash-loan, basis-crypto, impermanent-loss