What tptacek says is pretty much the gist of things. The issue for some is that because their order(s) are not reaching an actual exchange, the fill (price @ w

What tptacek says is pretty much the gist of things. The issue for some is that because their order(s) are not reaching an actual exchange, the fill (price @ which the trade(s)) is/are executed may not be the best, and that meaningful price discovery is hampered. Both may be correct, however, and I'm loath to say this, the average person lacks the capacity to really compete for the best fill price on a given trade. This is due to asymmetries (speed, data, etc.,). And so, generally, they are as tptacek says, "dumb money," who at best catch and ride a wave. Anyway, you may want to take a look at the following TD Ameritrade sites on fills[1] and order execution[2]. They aren't deep dives, just a flavor... [1] https://tickertape.tdameritrade.com/trading/stock-market-introduction-16061 https://tickertape.tdameritrade.com/trading/stock-market-int... [2] https://www.tdameritrade.com/trade/orderexecution/inc_faq.html https://www.tdameritrade.com/trade/orderexecution/inc_faq.ht...