So it sounds like 'automated scalipng'. I guess it makes them tons of $$. But to me it does not sound intellectually exciting - sounds more like an exercise in brute force computer technology.
it is basically automated scalping. Come up with an algorithm thats capable of averaging a fraction of a tick per trade, but do so much volume it makes money in the long run. I think the idea is that once you mathematically beat the game and become "the house", the law of averages is on your side and you want to pump as many trades through the system as possible.
It's just being called high-frequency trading by academics now. There's a whole bunch of papers coming out on high-frequency "descriptions" of the market, and there's entire conferences going on about market microstructure. Day-trading has a formal name now. It's true what people are saying in this thread -- all the big firms laughed at the day traders, but now they are nothing more than large scale day-traders.
Just like "Algorithmic Trading", it's used all over the place in different ways. Though, people around me define any "xxxxx-Frequency" terms as some sort of intraday trading, with: High Frequency = Trading based on the Bid/Ask quotes, Book, Depth, Multiple Pool Quotes, etc. etc. Mid Frequency = Trading based on the TOS (Tick). Low Frequency = Trading based on compressed data like bars. An example would be: "My model uses Low Frequency Data as a setup, triggered by Mid frequency and executed using High frequency data." or... "My model trades Low Frequency using a High-to-Mid Frequency Data"