DZone
Sparse files are files with “holes”. File holes do not take up any physical space as the file system does not allocate any disk blocks for a hole until data is written into it. Reading a hole returns a null byte.
Virtual machine images are examples of spare files. For instance, when I create a VirtualBox machine and assign it a maximum storage of 100Gb, only the storage corresponding to the actual data in the machine is consumed.
Source: DZone