What is DMDE?
DM Disk Editor and Data Recovery (DMDE) is a disk editor which can help you to understand NTFS. Its capable to view your hard disk sector wise, on MFT level, to disect mft attributes and to edit bytes on your hard disk.
Besides NTFS, it can handle other file systems such as FAT. Most functions are available by short cuts and it has a clean gui. Its recommended to use it along with Brian Carriers book about file system forensic.
The main functions you need to get an inside within the file systems are available in the free version.