go to dropbox.com. they have a video tutorial that shows you how to use it.
to directly answer, the storage is private. you can set up a folder and share it with other dropbox users if you choose to.
a discussion here about dropbox:
What size DropBox storage comes with the HTC EVO 4G LTE?
so we see the photos and such are not deleted. this is why i asked you to use this explorer app.
just attach your phone (make sure you turn off fastboot) to the computer. you should see a popup on your phone. select "storage device" or whatever it says (my memory escapes me right now--im watching Ralphie May on netflix...).
then go to the drive on your computer, and drag and drop files to your computer.
see here for more info:
Mount as disk drive (to transfer files, etc)
if you want to be truly wireless, I use wifi file explorer pro. https://play.google.com/store/apps/details?id=com.dooblou.WiFiFileExplorerPRO&feature =search_result#?t=W251bGwsMSwyLDEsImNvbS5kb29ibG91 LldpRmlGaWxlRXhwbG9yZXJQUk8iXQ
you can see your phones files and folders from your computers browser.