A computer's HDD drive may have some partitions. These partitions may contain any type of file system installed on them. NTFS stands for New Technology File System, is one type of file system that can be used on a partition.

Operating Systems Supported
Microsoft Windows OS since Windows 2000--this contains XP, Vista and 7 have supported NTFS.

Incompatibility
Most other OS--Mac for instance--cannot read NTFS by default. Updates can be downloaded to fix this, however.

Advantages of NTFS
NTFS contains many functions that were lacking in previous file systems, such as File Allocation Table (FAT) and FAT32. It permits for file encryption and user permissions, is more challenging to disk errors and uses disk space more capably.

Multiple Partitions
Because a partition is what get ready a HDD to have file systems, NTFS partition suggests that there are other partitions using different file systems. This possibly the case if a computer is used to dual boot a Windows OS and another OS such as Mac or Linux.

NTFS Partitions
You could also split a HDD into multiple NTFS partitions for use on only one OS. This is sometimes done to help with file organization--it makes separate drive letters within Windows--and to shrink the frequency of disk division.