When importing candidates or job openings, what field(s) is being utilized to look for duplicates?

When importing candidates or job openings, what field(s) is being utilized to look for duplicates?

Per the description:

1)  When I am importing job openings, what fields are being utilized to check for duplicates?  I just did my first test run of an import, and because many of the job openings had the same title (just descriptive of the task at hand), it picked up a bunch of duplicates that weren't actually duplicates.  Can you fill us in on what fields are used for duplicate checking?  (And it would be a great feature to add in the ability to select the criteria for duplicate checking!)

2)  When importing candidates, same question - which fields are being used to check for duplicates?

Thanks!