What: your figures should be self-contained (a CLEAR description should be included after the name).

Where: in documents and docuslides, recommended for your slides ONLY IF they are not too busy or the figure is not self-explanatory.

Why: people is multitasking even when they are reading your document… ejem… In other words, many people within your target audience will read your document diagonally and focus on your visuals. For presentations, it is quite likely that your audience attention will drop at some point; making your plots self-contained helps them to get back on track.

By the way, this page concurs…