Newbie Questions About Incremental Backup and Partial Backup

I have a 320GB Passport and have done one complete backup. I am in the process of doing a second backup.  Two questions:

(1) When I do this second backup am I just changing the original backup to reflect any changes since the first backup?

     (Is guess this is referred to as an “incremental” backup?) I assume that any time I do a new backup the result will be a fully updated adjusted backup and will take much less time to accomplish than the original.

 (2) “Data Backed up” shows a few hundred files short, so I get “Partial Backup Accomplished.” Why did this happen and what can I do fix it?  

     Thanks for help.


It will be an incremental backup, this means after the first backup only updated and new files will be addedd.

Partial backup means there were some problems when the software tried to backup a couple of files.

The files will be included on the next backup.

That mostly answers my questions. Thank you. But are you sure the non-backed up files will be included in the next backup? Why did it happen on the first incremental backup in the first place?

Pretty sure

The files are not backed up if other programs are using the files at the moment of the backup