If an overview gives a short summary of something, and a detailed analysis goes into a great deal of discussion, perhaps what you're looking for is something that is "simply" explanatory:
serving to explain
The explanatory section has as its heading "What the New Tax Changes Mean."
Alternatively (if you need a noun), an epexegesis:
additional explanation or explanatory matter
These words don't necessarily mean "intermediate" (because in depth explanations can be given) but they can be taken as such in context. Also, typically, unless you do provide an adjective for explanation, you don't often mean for it to be detailed.
The above is relevant to text.
If you are discussing diagrams or pictures, then this could be represented differently:
- summary view (a basic overview of something)
- functional view (enough information so that its actual use can be discerned)
- detailed view (details beyond just how it's used)