An investor’s directive to buy or sell securities when that directive is given to a broker, not to a trader working on the trading floor of an exchange. Exchange rules require off-floor orders, which are made on behalf of customers, to be executed before on-floor orders, which are made for exchange members’own accounts. In some cases, an off-floor order can be reclassified as an on-floor order where a conflict of interest might exist.
To be a floor trader, one must be associated with a member firm. Member firms pay hefty fees for the privilege of trading on the floor.
(its a crossing in common terms)
-investopeda