Logo vs icon: they are not the same thing
People ask for "a logo" when they need an icon, and the other way round. A quick, practical breakdown.
A client once sent me their "logo" and asked why it looked terrible as a browser favicon. It had the full company name, a tagline and a little illustration. At 16 pixels it was a grey smudge.
That's the difference in one story.
A logo is for recognition
It usually includes the name. It lives on your website header, invoices, packaging, the sign outside the shop. It has room to breathe.
An icon is for small spaces
Favicons, app icons, social avatars. No words (maybe one letter), one bold shape, strong contrast. It has to survive being tiny.
Can one be made from the other?
Often, yes. Take the symbol from the logo, simplify it, put it on a solid square. But "simplify" is the important word. Thin lines disappear. Small gaps fill in.
My habit now: design the icon at 32px first, then check it at 512. If it works small, it'll work big. The reverse is almost never true.
If you're making one, the [icon prompt](/prompts/app-icon-designer) shows the same symbol at five sizes so you can catch problems early.