The term of scalping is a commonly used terms in trading and can even have a negative definition as when scalping is not practiced by a licensed individual it can refer to fraudulent market manipulation; the term describes the practice of trading securities or foreign exchange (forex scalping) by using a form arbitrage in small gaps that might be created by the bid ask spread as it is widely known.
In this sense it is the practice of purchasing a security on a personal account and immediately or very shortly after recommending the security or currency for a profit to a third party upon rise of the market in an effort to accumulate profit from the recommendation.
It is only reasonable that forex scalping and financial scalping is a sensitive practice which can be easily abused which is the primary reason the supreme court of the United States has made it a fraudulent activity for individuals that do not posses an investment advisor license to practice scalping after being traced to be commonly abused by individuals taking advantage of people in their immediate circle which they could easily influence.
Scalpers as the term describes operate as market makers; their goal is to manage and scalp the market at a given time in their favor and therefore benefit from making the spread by buying a foreign currency at a bid price and selling the currency at an ask price. The overall tactic allows margins for profit even in the case when bid and ask do not move as long as demand is available to trade market prices. The term scalper is often translated to market maker when the extent at which the practice is performed is large.
The basics principles of forex scalping start with the principle that scalpers do not hold overnights as they do not risk moving into market fluctuations which can cause huge losses or even decreases; additionally scalpers trade in large volume as the pattern in which they engage does not allow large margins of profit which means in order to sustain a respectable profit they need to trade in volume. Since the profit obtained per share or contract is very small due to its target of spread, they need to trade large in order to add up the profits.
Scalping is not suitable for large-capital traders seeking to move large volumes at once, but for small-capital traders seeking to move smaller volumes more often.