This isn't my best area, but I'll try anyway!
Okay, so the 4 parts of working memory are the phonological loop, the visuo-spatial sketchpad, the central executive and the episodic buffer, yeah?
The phonological loop, the sketchpad and the episodic buffer are the
storage systems.
The phonological loop is the storage system for all the auditory, speech-like information. This is like, the little voice in your head when you read something or is repeating what you want to write in an essay. It subvocally rehearses the information in a kind of 'loop' and stores it for a little while.
The visuo-spatial sketchpad is like the canvas in your head where you visualise everything. It's the storage system for the visual and spatial information. So if you close you eyes and imagine your journey to school in the mornings, and what your school looks like, that's your visuo-spatial sketchpad.
Okay, so then there's the episodic buffer, which is the one Baddeley added in a little later. This is the one that allows everything else to communicate with LTM, and it also binds information from LTM, the phonological loop and the sketchpad into a little scene (episode) with time-sequencing. Its main function though, is to retrieve info from LTM and feed it to the central executive for manipulation or problem solving etc.
Then there's the central executive, the 'boss' system. This one doesn't store anything, it directs the slave systems (the other 3) and co-ordinates their actions, using the information they've stored to make decisions and problem-solve. It directs attention towards things, and recognises what information needs to be retrieved so it can carry out a task and manipulate the information and orders the episodic buffer to get that information.
Did that help at all?