What is Run VUSER as a thread and Run VUSER as a process?

If you select run vuser as a thread the driver program is shared for every vuser. I,e if 100 vusers are running at the same time, then all the 100 vusers will point and share the same driver program so that lot of memory will be saved. Where as if you select run vuser as a process, then the driver program will be loaded 100 times so that each vuser will use the driver program independently thus taking lot of memory.