Short-term memory according to Atkinson and Shiffrin (1968) is our working memory. STM has two functions. It helps us from, and update a picture of our world on a minute-by-minute basis, and also helps us think and problem solve. STM has a decay rate of between 15-20 seconds. We must use STM information in this time otherwise it is lost to us.
Found on http://www.gerardkeegan.co.uk/glossary/gloss_a.htm