These two segments seem very similar, but there is an important difference.
Unpaid Segment
This is the default Segment in the rollup.
The name pretty much says it all: this will look at everything that is not a paid result.
So, if you are ranking in any Google Features like People Also Ask boxes, product results, Top Stories or almost anything else, this segment will include those results.
Organic Segment
The organic segment only counts traditional, blue-link results and ignores all the other search engine features.
So, if you are ranking in the Top Stories or a Video pack or some other feature, it will not be included in these results.
Exploring Further
You can see how Nozzle labels each result in the Single Keyword Dashboard.
On any dashboard, you can simply click the keyword you want to analyze and you will go to the Single Keyword dashboard for that phrase.
Scroll down to the SERP Snapshot at the bottom.
Click the +Add Columns button and then start typing “Organic”.
Select Organic>Is Organic.
(If you only want to see this label, you can click to clear the other metrics from the view.)
"Is Organic" will now appear in the box on each result, and if our system identifies it as an organic result, it will have a green checkmark next to it.