Working Memory refers to the temporary storage and manipulation of the information necessary for complex cognitive tasks such as language comprehension, learning and reasoning. Working memory, which is generally considered to have limited capacity, requires the simultaneous storage and processing of information. This ability stresses the manipulation, rather than passive maintenance, of information.
Example: While at the supermarket, you realize that you left your credit card at home and that you have $50 in cash. You look at your cart and add the prices of all the items there while REMEMBERING the overall sum. You then conclude that you cannot buy anything else and move to the checkout.