The file system introduced with Windows NT 3.1 was NTFS. Microsoft designed NTFS as a more secure and reliable replacement for older file systems used by DOS and consumer Windows systems.
Windows NT 3.1 launched in 1993 for workstations and servers. NTFS introduced features important in business environments, including file and folder permissions, support for long file names, improved recovery after crashes, and journaling to help protect the file system from corruption.
Windows NT 3.1 also supported FAT16 and HPFS for compatibility, but those systems lacked many of NTFS’s security and reliability features. NTFS has remained the standard file system for Windows installations, although it has gained many capabilities over time, including encryption, compression, quotas, and support for very large volumes.
A common mix-up is FAT32, which arrived later as an enhancement to the FAT family and became common on consumer versions of Windows. ReFS is also a Microsoft file system, but it was introduced much later, with Windows Server 2012.