What counts as "commercial use"?

The Creative Commons licenses define NonCommercial as use that is "primarily intended for or directed toward commercial advantage or monetary compensation." That covers the obvious cases — selling a product that contains the work, running ads against it, etc.

Edge cases get fuzzier: a free podcast with a sponsor, a non-profit running a fundraiser, a teacher uploading material to a paid course platform. When in doubt, contact the author directly to ask.

If you want to allow all uses unconditionally, choose CC BY or CC0 instead of an NC license.