/data/app
Say you download and install an app from Google Play store. The "apk" is placed in the /data/app folder. All application apk files are located in /data/app (non-system-apps) and the file names are not visible without root permission. The file permissions on the app folder are 771 (chmod 771) meaning that only the executable flag is set for non-privileged users. Without the read permission set, it is not possible to list the filenames in the folder, unless you have root. The installed application apk files can be extracted if the name of the file is known.
- User installed apps apk's are stored at /data/app
- System apk's are stored at /system/app
Some workarounds to view the filenames in the /data/app folder without having root exists using "adb". They vary depending on the Android version of your device. It is simply so much easier if you have root access to your device. See the discussion of this page to read about the workarounds.