Internal memory or better known as phone memory is a storage area for the Android OS. All system data and applications are stored in internal memory. In addition, sometimes there is also personal data stored in the memory, such as photos, music and videos. Erasing or formatting Internal memory as a whole is a very risky action, because indeed the Memory contains the Android OS. So, if you delete it as a whole, your Android Smartphone will no longer be used, unless you have backed up all system data.