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For example:
Does 80% of the code come from 20% of the functionality?
Do 80% of bugs come from 20% of features?
Does 80% of software complexity come from 20% of the functionality?
Definitely 80% of the bugs will come from 20% of the features. 80% of the usability and attraction is also from 20% of the features, but not necessarily the same ones.
Perhaps relatedly, about 70% of all software work is diagnosis and debugging. So a small subset of (maybe not so important) features causes most of the overall work in the project.