Working memory, the more contemporary for short-term memory, is conceptualized as an active system for temporarily storing and manipulating information needed in the execution of complex cognitive tasks such as learning, reasoning and comprehension. There are two types of components, and they are storage and central executive functions. The two storage systems within the model (the articulatory loop (AL) and the visuospatial sketchpad or scratchpad (VSSP) are seen as relatively passive slave systems primarily responsible for the temporary storage of verbal and visual information respectively.
The most important, and least understood, aspect of working memory is the central executive, which is conceptualized as very active and responsible for the selection, initiation, and termination of processing routines including encoding, storing and retrieving.
Source: The University of Alberta's Cognitive Science Dictionary
