How does slippage work?

When buying or selling a forex or CFD product, your order is intended to be executed at the best available market price, but the actual execution price may be better, equal to or worse than expected. 

In a fast-moving market or less liquid market, this commonly happens because market quotes don't reach the intended level or the price moves too swiftly  for the trade to be executed precisely at the expected price, resulting in Slippage.