The visibility of your content is defined by two factors: Privacy Settings & Safety Levels.
Privacy Settings
Privacy Settings let you control who can see your content, regardless of the Safety Level.
You can set each item’s privacy to be seen by everyone, no one, or just your Flickr contacts marked as Friends or Family.
If someone can't see an item in your Photostream you will need to make sure that the correct permissions have been applied.
If you are wanting to share private content, see how to create a Guest Pass.
Safety levels
Safety levels are used to define the kind of audience your content is intended for.
Please note that all content must be properly moderated, regardless of the Privacy Setting. This includes posts marked as Friends and/or Family and Private.
The Safety Levels available are:
Moderate & Restricted content are only visible to members who modify their SafeSearch preferences to see that level of content. Visitor’s not logged into a Flickr account will only see the content if it has the Safety Level set to Safe.
Note: Setting the Safety Level for your content does not impact the Privacy Settings. Read more about Safety Levels and learn how to set them.