This option is new to Lightroom CC, and Im still finding the right way to use it in my workflow. Basically, it gathers pictures together based on the faces it can recognize in the image. The more I think about it, the more I see some powerful uses for it.
Enter the People view using the icon at the bottom of the Library screen (press T to show the tool bar) or by pressing the O key (P is already taken for flagging a picture as a pick).
Lightroom begins automatically recognizing faces and stacking pictures together with the same faces; the same picture will be in multiple stacks if it has multiple people in it; double click on a stack to see all the pictures in it. Now, just click on the ? under each stack and enter the name of the person shown. now each stack moves in to the category at the top of Named People. Lightroom now uses that name as a keyword, so over time, I could search the whole catalogue for people based on their names and Lightroom finds them for me. Thats pretty cool.
Lightroom even gathers the people it thinks it knows and puts a ? after their names to ask its correct, and you just click the check mark or the x. Again, very cool!
The thing is, I pretty much know who my clients are, and I keep them organized by name in the folder tree, so Im not usually trying to search for anyone by namebut maybe I will start doing it. Im thinking of three instances when it could be really useful: weddings, big family groups, and finding my own kids pictures.
For weddings, Im thinking itll be handy because itll gather all the pictures of the bride together, or the grandma, etc, and when I show the bride pictures she could ask me to see all the pictures with her and the groom and the grandma, and I could do that using the keywords instead of searching around in the grid view.
Similarly with family pictures, I often photograph three or four generations together. Im quite good with names and will know everyones names the by the end of a shoot; but if you ask me three months later (which is often how long it takes a big family to get their orders together) I may have forgotten a few names. If I use the People view to name everyone right after the shoot, then itll make me look like a more attentive and caring photographer because I can review everyones names before the sales session.
The thing about pictures of my daughter is that my Drobo is littered with them everywhere; they could have been made at any time, and on any number of cameras. I may walk in the door after a shoot and see her doing something photographable and add a frame or two of her to the the same memory card from the shoot. People view can help me gather these pictures from all over my hard drives and have them handy when its time to make an album.
Like I say, Im refining my workflow to try to include this tool. Its pretty incredible that this caliber of tool is now in Lightroom.