what is the different between thick and thin disk in vmware Or, thick-provisioned and thin-provisioned disks

what is the different between thick and thin disk in vmware Or,  thick-provisioned and thin-provisioned disks 

thick-provisioned disks are created with the entire size of the disk pre-allocated on physical storage at the time the disk is created. This pre-allocation means that creating a 50GB virtual disk actually consumes 50GB of physical disk space on your drives.

 thin-provisioned disks are created with the amount of physical disk storage used by a virtual disk is equal to the amount of actual data on that disk. If you create a 100GB disk but only use 20GB of that disk, the actual disk consumption on your physical drives will be 20GB.

Note: Versions of ESX prior to 4.0 were only capable of creating thick-provisioned disks.