Day trading is traditionally defined as buying and selling stock, options, or commodities during the same trading day and be have your positions closed by the end of the trading session. In the past, day trading had been reserved for financial companies and professional investors. A large percentage of day traders work for investment firms or are specialists in fund management. With the advance of technology, day trading has continue to grow among the casual trader working from home.
This often means trading shares of companies that have just released breaking news, reported earnings, or have another fundamental catalyst that is resulting in above average retail interest. The type of stocks a day trader will focus on are typically much different from what a long term investor would look for. Day traders acknowledge the high levels of risk associated with trading volatile markets and they mitigate those risks by holding positions for very short periods of time.
These developments heralded the appearance of "market makers": the NASDAQ equivalent of a NYSE specialist. A market maker has an inventory of stocks to buy and sell, and simultaneously offers to buy and sell the same stock. Obviously, it will offer to sell stock at a higher price than the price at which it offers to buy. This difference is known as the "spread". The market maker is indifferent as to whether the stock goes up or down, it simply tries to constantly buy for less than it sells. A persistent trend in one direction will result in a loss for the market maker, but the strategy is overall positive (otherwise they would exit the business). Today there are about 500 firms who participate as market makers on ECNs, each generally making a market in four to forty different stocks. Without any legal obligations, market makers were free to offer smaller spreads on electronic communication networks than on the NASDAQ. A small investor might have to pay a $0.25 spread (e.g. he might have to pay $10.50 to buy a share of stock but could only get $10.25 for selling it), while an institution would only pay a $0.05 spread (buying at $10.40 and selling at $10.35).
Scalpers need to be disciplined and need to stick to their trading regimen very closely. Any decision that needs to be made should be done so with certainty. But scalpers should also be very flexible, because market conditions are very fluid and if a trade isn't going as expected, they'll need to fix the situation as quickly as possible without incurring too much of a loss.
The first key to successful swing trading is picking the right stocks. The best candidates are large-cap stocks, which are among the most actively traded stocks on the major exchanges. In an active market, these stocks will swing between broadly defined high and low extremes, and the swing trader will ride the wave in one direction for a couple of days or weeks only to switch to the opposite side of the trade when the stock reverses direction.