The i10-index is created from Google Scholar and found in Google's My Citation profile. Introduced in July 2011, the i10-index is the number of publications with at least 10 citations. Although it is only used by Google Scholar, it is another metric able to be used to measure scholarly outputs.
The advantage of this metric is that it is free and easy to use, and is very straightforward to calculate.
The disadvantage is that it is only used in Google Scholar.
An example can be seen in the My Citations profile for Charles Darwin: