With a final click on the digital request shot into the ether. A few seconds later, a satisfying ping echoed in the room. The status changed from "Open" to "Filled."

Being a cautious investor, Leo chose a for $24.85. He wanted to ensure he didn't get caught in a sudden price spike. He entered the quantity—200 shares—and hit "Review Order." The Confirmation

He clicked the button, and a trade ticket popped up. He had to make a choice: