In a nutshell
Scalping' is the process of capitalising on minor, short-term price changes within an Exchange market to make small profits, with relatively low risk. It involves offering bets on both sides of an active market selection and hoping to be matched at slightly different prices.
How does it work?
Scalping is a short-term "in and out" trading strategy. The aim is to take a very small profit from minor price movements.
In order to successfully complete a scalp, you need to place two opposing bets against each-other, usually one or two price tick increments apart, in order to guarantee a profit on the selection.
This can be achieved by offering a back price that is slightly lower than market price, waiting for it to be matched, and then taking the slightly higher lay price.
Software can then be used to ensure an even return across all outcomes. Highly popular events with large betting volumes are most suited to scalping methods.
A Scalping example
Manchester City are trading at [2.0] to win a game.
You offer a back bet of £200 on Man City at [2.02], hoping for a touch of market movement, and a similar Lay offer of £200 at [2.00].
Once both offerings are matched, you will have a potential return of £400 if Man City don't win, but a return of £404 if they do win (excluding commission). So, Man City are a "green" selection for £4, without any liability.
Software can be used to "green up" your book, and spread that £4 potential profit evenly across the three selections in the market.
"Scalps" such as these can be done repeatedly in a liquid market in order to build your overall profit on the event.
Advanced trading software is normally always used by players who wish to scalp, due to the added ease of placing bets and removing risk from your book.