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Forgive me if this is a really simple question, but I just can't seem to figure it out: what's the difference between a differential and incremental backup?

The guide says
-Incremental backup (only backs up the data which has changed since the last backup)
-Differential backup (only backs up the data which has changed since the last full backup)

If the first backup is a full backup, then shouldn't the differential behave just like the incremental since data is going to change since the initial/full backup? Can someone clarify this for me?

Thanks.

The guide is correct.

Let's say that backup #1 is a "Full Backup".

Then, a few days later, you perform backup #2 as an "Incremental Backup". In this case backup #2 will only include files that have changed or been added since backup #1.

Now, a few days later, you perform backup #3 as a "Differential Backup". In this case backup #3 will include files that have changed or been added since backup #1 (the last full backup).

But, if backup #3 was an "Incremental Backup", it would have only looked back to backup #2 to determine which files to backup.

So, ...
Differential backups always look back to the most recent "Full Backup" to determine which files to backup.

Incremental backups only look back to the most recent backup "Full or Incremental".

I hope that helps.

After reading that a few times, the lightbulb finally came on. Duh

Thanks treemana.

You're welcome. It was a little difficult to explain. I'm glad the lightbulb finally came on!