Google+ and Picasa Web Albums: Name tags
When you sign up for Google+, all existing name tags in Picasa Web Albums remain unchanged. For new tags created in Google+ or Picasa Web Albums, here are the essentials:
Your friends can tag your photos
Name tags are better with friends. People that you've added to your Google+ circles are the only ones that can add name tags to your photos (if they have access).
People tagged receive access to the album
The person tagged will be given permission to view the photo and the related album, so they know where they were tagged. They'll also have the ability to reshare the album with others. You can lock the album in Google+ to disable resharing and also remove people from the album's 'Shared with' list at any time.
You'll receive an email letting you know you've been tagged in a photo. By default, name tags by people in your circles are automatically approved. You can view or remove tags at any time on the photos homepage in Google+ as well as the Photos tab on your Google profile. You can also update your settings to manually approve every name tag. When a tag is approved, the tagged photo is posted to the Google+ stream.
Name tags are visible to people that can view the album. Approved tags link to your Google profile. Unapproved tags are still visible on the photo, but they don't link to your profile. In addition to appearing on the photo itself, photos of you with approved tags will be displayed on the Photos tab on your Google profile and the photos homepage in Google+.