How do you label individual photos?

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What system are you running?

Are these photos in a Photos library?

What do you mean by "label", mark as favorite or add keyword or …?

By memory book do you mean a photo book by one of the 3rd party online firms, i.e. PrestoPhotos or Mimeo Photos?

What do you mean by label? Add text to the image or identify the photo to make it easy to add to an album and create the photo book?

Don't know what you mean by label.