"Offline" means "not connected."
The most likely meaning in the context you describe is that some of your pictures are stored either on an external drive (that is not turned on or is not connected to your computer) or in some "cloud" storage service and your computer is either not connected to the Internet or you are not signed into that particular service.
My guess is that you have Windows Photo Gallery (or Windows Live Photo Gallery) installed on your Windows 7 computer. You can see a general description of this program here: https://en.wikipedia.org/wiki/Windows_Photo_Gallery
Assuming that you have Photo Gallery, when you run it (on the Windows 7 computer), you should see something like this:
The left pane, which is just like the left pane in Windows Explorer (the Windows 7 file manager), shows where Windows Photo Gallery "looks" to find the photos that it displays.
Enlarge the Windows Photo Gallery window so that you can see all of the folders in the left pane. If you have to scroll in order to see all of the folders in the left pane, collapse some of the subfolders by clicking the black triangle next to the containing folder (e.g., if you click the black triangle next to "Public Pictures," you won't see its two subfolders, NVIDIA Corporation and Sample Pictures).
Once all of the remaining folders are visible, take a screenshot of the Photo Gallery window and include it in your next post here. For directions, see https://answers.microsoft.com/en-us/feedback/forum/fdbk_commsite-fdbk_getstart/how-to-include-a-screenshot-in-your-post/2594b08e-32a3-476a-85a6-b021181be7e4
