High Frequency Trading

Here is a post by a fellow Blogger Tyler Durden, I like him a lot, and his whole Fight Club theme aint bad either 

In very broad terms, high-frequency trading (also known as HFT) refers to the buying and selling of stocks at extremely fast speeds with the help of powerful computers. Using complex algorithms, these computers can scan dozens of public and private marketplaces simultaneously, execute millions of orders a second, and alter strategies in a matter of milliseconds.^[1] In the U.S., high-frequency trading firms represent 2.0% of the approximately 20,000 firms operating today, but account for 73.0% of all equity trading volume.^[2]

Here is the link