InDesign can only open InDesign files. If you start a new InDesign project, and then go to File -> Place, you'll find that you can place many different kinds of file into InDesign. But InDesign can't be used to edit jpegs (Photoshop is the correct app for that), and while you can certainly import Word files into ID, the proper tool for editing Word files is, of course, MS Word.
Maybe if you told us a little bit more about what you're trying to do, we could give you better guidance.
Correction: ID can open other file types, including IDML, InDesign templates, InDesign Book files, old PageMaker and Quark files, and... I must be missing something. Ha! Joboptions files. I don't think that this is what you were asking about, though.
Thanks Joel: Wonderful insights, much appreciated. I was told by an ebook
publisher that after uploading my Word doc file to them, I needed to
resubmit the entire file in what is called a "fixed format" and I
researched enough to understand InDesign can do this. In essence, I have a
Word doc with 100 color images (a mix of portrait and landscape, thus the
need for the "fixed-format"). I'm reloading a new Word doc. file with 100
landscape (or horizontal images) but will need to make it a fixed format
using InDesign....I can probably do it after studying a tutorial by Lynda
on YouTube. However after I was all ready to roll with this , I then come
across this next stumbling block.
There are a few different ways to make a fixed-layout epub, but to be quite honest a) I don't know much about them as I have only dabbled in epub outside of a few specific areas, and b) InDesign is not a tool that you will be able to learn to use quickly and easily - even if it is easy to create that form of epub with InDesign. I do see that it's hard enough to do fixed-layout epub in InDesign that someone can make a commercial product that claims to "Convert InDesign Books To iBooks in One Click!" The first part of that (learning how to make books in InDesign in the first place) has a pretty steep learning curve by itself. So I don't know that InDesign is the best tool for what you are trying to do.
My suggestion to you is that you start a new thread with a title that will grab the eyes of the forum regulars who are more conversant with this topic (i.e. "Need to make fixed-layout epub, is InDesign the right tool?"). Steve Werner often points people towards the MobileRead forums, which I've found to be a very useful resource. But this thread title isn't going to haul in the majority of the forum regulars who know a lot about this topic, and It's Deeper Than It Looks.