i'm about to go to bed so this is a straight copy from my notes (which i believe melaniej posted on here originally.)
Working memory is the three part system of STM that is used for the temporary storage and active manipulation of information during complex cognitive tasks such as learning, comprehending and reasoning. It has three components; the phonological loop, the visuospatial sketchpad and the central executive.
The phonological loop is the area of working memory that holds sound based information for approximately 2 seconds. It contains two subsystems the articulatory control system and the phonological store. The phonological store holds speech for approximately 1.5-2 seconds and the articulatory control system holds information by sub-vocalising it.
The visuospatial sketchpad is the area of working memory that holds visual and spatial information for manipulation such as remembering shapes and colours, or the location or speed of objects in space. It is also involved in tasks which involve planning of spatial movements, like planning one's way through a complex building. When for example, you are watching TV, and you have put a glass down next to you, you can reach out and still know where it is while you are focussing on the TV due to your visuospatial sketchpad.
The central executive monitors, controls and integrates information from the verbal and visual storage systems, as well as information received from long-term memory. It plays an important role in working on the information held in the other two subsystems. It’s also responsible for suppressing irrelevant information from our conscious thinking and involved with like decision making and planning.
if you want more explanation have a look at the eriny's unit 4 notes on the vcenotes.com home page.