The kind that we can generate here in Word is called a document ToC. We like to call that a 'Hot Dog Menu' because it looks like hot dogs, strangely enough. There's sometimes a little set of horizontal bars up in the top left hand corner. The navigational ToC, just so you know, is the thing that typically appears on the side of the screen when you tap the screen and it shows you all of the different locations in the ePub. And remember that here in Word, we can only go as far as generating the HTML.
It's generated at the time the actual ePub file is made. And it's something that you can't do in Word. There are two kinds of tables of contents available to ePub files.