You can tag the people in your photos so that they're easy to find.
Once you've added a tag of someone, his or her name will be saved as an auto suggestion for the future. You'll also see this person's name as a category under the Faces tab in the menu on the left side of the album viewer, allowing you to quickly find all the photos you've tagged this person in.
NOTE: If you add face tags to an image, you will only be able to see them in your account. If you share the image(s) with another user, they will not be able to see the face tags that you had created.