Aren't viewable by others, except those you've shared the kahoot with directly.
Are viewable by others on the "Public Kahoots" page.
There are 2 ways to change a kahoot's privacy setting:
1. Under "My Kahoots" > Created by me you can hover your mouse over your kahoot to see a message saying "Make public?" or "Make private?" appear. Click on this.
2. While editing a kahoot's description, you can change the "Visible to" field to "Only me" (Private) or "Everyone" (Public).