High-frequency trading (HFT) covers such a wide path of trading — different parties participate and different parties are affected in different ways. I wanted to put this out there as a starting point. Hopefully the comments will help further educate us all.

1. Electronic trading is part of HFT, but not all electronic trading is high-frequency trading.

Trading equities and other financial instruments has been around for a long time. It is Electronic Trading that has led to far smaller spreads and lower actual trading costs from your broker. Very often HFT companies take credit for reducing spreads. They did not. Electronic trading did.