First Time User of WD Backup software

I have read all the user manual material but cannot find an answer. I have a passport prtaable drive that I use to back up my Windows laptop,

 I am using the WD sofware that came with it. When I did the first back up, I set it to backup all types of files and I assume it backed up the entire HD of my laptop.

My question deals with subsequent backups. Do subsequent backups only create a backup up of each specific file that has been modified since the previous backup OR just do an entire backup of all files, changed or not, once again.

If i set it to maintain 3 copies, depending on above answer, does it then keep the last 3 copies of only the modified files or 3 copies of the entire laptop.

Again I am using the backup all files setting for each backup.

If it backs up the entire source every time, is there a way to only bacup modified files?


WD Smartware will not backup your entire computer. System files and programs will not be included. 

The WD Smartware software will only backup your files and it will backup any new file as well as any update made to a previously backed up file.

If you have set the software to keep 3 copies of each file it will keep 3 copies of every file that it has been backed up.