A public comment or note allows donors to express their motivations for supporting certain causes or organizations, so other donors on Daffy are inspired to support that charity too.
When you make a donation and leave a public note on Daffy, you're not just supporting a cause you care about, you're also inspiring others to do the same. Your public note can help others discover new organizations, understand why they matter, and feel inspired to give as well.
A public note is publicly viewable on your profile and the non-profit’s Daffy page, and is different from a 'Private Memo' which is only visible to the charity and used by donors to communicate the intent of their donation directly to the charity.
You can see how your note appears in the Donation Letter here.