Guest Passes let you share your photos that aren't public. Anyone can see your public photos anytime, whether they're a Flickr member or not. But! If you want to share photos marked as friends, family or private, use a Guest Pass. If you're sharing photos from a set, you can create a Guest Pass that includes any of your photos marked as friends, family, or private. If you're sharing your entire photostream, you can create a Guest Pass that includes photos marked as friends or family (but not your private photos). Learn more about Guest Passes![?]
What are tags?
You can give your uploads a "tag", which is like a keyword. Tags help you find things which have something in common. You can assign up to 75 tags to each photo or video.