What wash trading is
Wash trading is buying and selling the same contract on both sides of a trade, so ownership never really changes. The trade prints, the volume counts, and nothing moved.
The purpose is usually to manufacture a signal: volume that suggests interest, a price that suggests agreement, or activity that qualifies for a reward program. It is prohibited on regulated venues and it is a recognized manipulation pattern everywhere else.
Why on-chain markets make it visible
On a public chain, funding is traceable. Wallets that trade almost exclusively against each other and were funded from a shared source form a pattern that is visible without any special access, which is a stronger position than a traditional venue where the same activity is internal.
Detection is still probabilistic. Related wallets can have innocent explanations, and unrelated traders can produce similar patterns by coincidence. The honest output is a statistical flag with the evidence attached, not an accusation.
Where 0xinsider uses it
The insider-detection guide covers the flag classes and what each one is and is not evidence of. Flags are anomaly signals with the wallet, market, and timestamp attached so the reader can check them; 0xinsider does not label any trader a manipulator.