When you choose to share something with the Public (e.g. when you select Everyone from the audience selector), it’s considered public information. If you share something and you don’t see an audience selector or another privacy setting, that information is also public.
Content other people share: If other people share info about you, even if it’s something you shared with them but didn’t make public, they can choose to make it public. Also when you comment on other people’s public posts, your comment is public.
Pages, Groups, Blogs, Jobs, Market, & Satellite Profiles: These are public spaces. Anyone who can see your post can comment. For more see Community Feed,
Don’t forget, you can control who you share information with in settings. Please take time to get to know the settings of each profile you create.