Shopify stores your file uploads in the Files page. You can add these files to your products, collections, pages and blog posts.
You can upload files in all the usual text formats (i.e. .pdf, .txt, .doc etc.) and images as: .jpg, .gif or .png.
The Files page of your admin is where you can:
Upload new files.
Scroll through all of the files you have uploaded.
Click the garbage can icon to remove files.
Click on image links to edit them.
Copy URLs to link to the files from your product, collection, blog post, page, or to link to from somewhere outside Shopify like email or social media.
The images are stored internally as part of our content distribution network (CDN). We remove images and make different sizes of the images as we need to. For instance, if you look at blackmilk clothing, the image url for the main product image is on this product http://blackmilkclothing.com/products/3d-ribs-swimsuit
As you can see, the file name is has been modified by the system to show the proper size we want. You don't direct access to these files.
Hope that clarifies things!