HFT stands for High Frequency Trading; it is the use of algorithm to trade stocks, options and other securities in very short time (can be nanoseconds to few hours)
High Frequency Trading (aka HFT) is a rather specific and special style of speculative trading, based on quantitative models that benefit from extremely fast order execution or on an immediate removal of a pending orders and having rather short position-holding times.
While media have illustrated HFT traders as evils for the market, serious quantitative analyses, incl. the research papers from former FED's market oversight-body consultants, have brought the very opposite view on HFT's-role, both during flash-crash events and during regular market operations.
Similarly, there were documented cases, when an erroneous algorithm-trading engine have caused damages exceeding hundreds of millions USD before the fault has been detected and isolated.
It is also fair to state, there are markets, where HFT can benefit from an advantage in a fast order-execution/-cancellation, whereas there exist also a principal market organiser, where no such advantage is ever available (by design), as a corner-stone principle of the market that strives to eliminate an unfairness in "buying" such advantage and thus creating an unequal-access to the same market.
