system
A chat on subreddit /r/wallstreetbets
human
They actually don't execute the trades but give a perception that a trade was executed.  Knowing a majority of customers will lose money and they pocket the 'loss' from the fake trade.

gpt
thats not legal correct? 
  
 or is it ok if they pay out when they are wrong? 'mirror' the trade? if they disclose it in TOS or something. 
  
 we know etrade finds trade pairs. so if bid ask on market is narrow and two etrade users put in orders to buy/sell for greater/lower they just can sell at the market and collect the difference.