Reparse point file attribute is used by file system as directory junction points and volume mount points to extend functionality of input / output subsystem. Reparse point attribute specifies that a file or folder represents a set of user-defined data. The format of this data depends on the software that stores the data and can be understood both by this software and file system filter. When the file system opens a file with a reparse point attribute, it runs a file system filter identified within the reparse tag.
Reparse points are used to implement Remote Storage and NTFS links. When an actual data is moved away to another volume or data storage device, there still remains reparse point that shows as to where from this data should be taken. To software this process is fully transparent, i.e., all the necessary tasks are done at the file system level.