Beginner question

I am looking for a program to build a website on my Mac for a client that uses a PC/Windows, a cross-platform. Once it is up and running she will upload new photos and add new content. We would also like to have a "store" where people can buy items using a credit card or PayPal. Also drop-down menu and what type of graphics are used? Jpeg, PDF, eps, tiff? After looking at this site I notice Revolution and Evolution, are these extensions of MODx program? As a total beginner what would you suggest I start with?

Evolution and Revolution is the two versions of MODX that is available. They´re quite different but are built on the same idéa of how a CMS/CMF should work.
A good way to start is to look at the MODX-webpage, for example here http://develop.modx.com/develop/revolution/quickstart/, to get a grip about it.

As a total beginner, you should also look up some good books and/or webpages about general web development to be able to choose the right platform for you to work with.

For a simple site like that, I would recommend Evolution. It has some very nice gallery add-ons (my favorite is Easy2Gallery). It also has very nice front-end editing features.

The best way to handle a store is to subscribe to FoxyCart, but there are other options as well. I rather like the JQuery JShop application.

You can look over my site, which is Evo; the guest manager login is guest - guestuser. I also cover most of how Evo works in the MODx From the Inside section of the site.

Boy I'm really confused, how does FoxCart, etc. work? Do they handle the credit card end when someone buys something? Do they set up the color and size buttons, take care of gift cards, the secure shopping. Once you click on Your site is evo? When I look at this site it's entirely online shopping, like I said I'm just totally confused.

The catalog and cart are done with MODx. Once the customer is ready to check out, then FoxyCart handles the checkout and payment process.

OK so this is how much of a beginner I am. I've downloaded the Modx 2.2.0 folder..... now what do I do? I don't see any type of manual, did I download the wrong thing?

Well, the first thing you should do is read the manual http://rtfm.modx.com/display/revolution20/Basic+Installation

I don't even know what it means by loading your web browser and running the setup script by navigating to the setup/ folder.

Sorry but I did say I was a "beginner"......

Open your web browser. In the address bar, put "http://yourdomain.com/setup" (without the quote marks).

In my case, since I have MAMP installed on my Mac, I use "http://localhost/setup" while on my hosted development server I put "http://dev.sottwell.com/setup"

So there is no way to try out this software before I have a domain/website? If I already have a website what's the point of getting this one?