As technology evolves, things change. Android is no different. With recent Android releases such as Honeycomb, Ice Cream Sandwich, and Jelly Bean, there have been quite a few changes. On many devices, USB Mass Storage changed to MTP, widgets became part of the default launcher’s app drawer, and everything went from green and orange to blue. One change that many don’t know about is Google’s new way of handling storage on many devices.
I’m writing this page because there seems to be a lot of confusion about how many of the newer Android devices work. Starting in Honeycomb 3.0 with the Xoom, Google changed the way that they handled storage. Instead of having a “data” partition with your apps and a separate “sdcard” partition for storage, Google started giving you a single, very large data partition. Inside /data is a folder at /data/media that contains all of the contents of what you think of as your internal sdcard.
This can be so very important for a number of reasons. For example, this is why TWRP ignores the /data/media path when wiping data. The big reason, however, is so people are aware. If you wipe your /data/media, you’ll be wiping your Nandroid backups, the ROM you were planning on flashing, your app backups, your photos, and everything else that usually stays safe on your SD card. So if you boot into TWRP to flash a ROM and you format /system, wipe /cache, and wipe /data including /data/media, you’re in trouble. You have no system to boot to, you have no ROMs to flash, and no backups to restore. The only way back from that is to ADB push a ROM onto your device to flash.
For the full explanation on the new storage system, how it relates to MTP, and much more, check out Dees_Troy’s explanation on the official TWRP website.