I think this might be a second language thing. My understanding of index would be the one you have at the beginning of the book, with the chapters and their page numbers. The reverse index appears at the end of the book and lists topics and the pages where they appear.

For example, in the index you'd have chapters:

    3. Data structures 25
    [...]
    7. Graphs 154

And in the reverse index:

    trees: 25, 154

But maybe those are just the table of contents and index?

Ah, I see. Those are indeed the names I'm accustomed as a native anglophone to use for those respective sections.

edit: Commenting before coffee, I mixed up "anglophile" and "anglophone," intending the latter.