Thin provisioning vs Thick provisioning

Thin provisioning  - In this format, the size of the VDMK file occupies on the datastore only the size of how much it is used. For example, if you create a 500GB virtual disk, and place 100GB of data in it, the VMDK file will be 100GB in size in the disk.

Thick provisioning  - If you create a 500GB virtual disk, and place 100GB of data in it, still the VMDK will appear to be 500 GB at the datastore filesystem, but contains only 100GB of data on disk.