Is this a Lightroom question?
If so, you can't select objects in Lightroom, if I am understanding you properly.
Like outline an person & make changes only to it.
You could use the adjustment brush to only make changes to an object, but this is not "selecting" the object in the normal sense of the word. And there is no "outline" created. And it would be easier to do in Photoshop or Photoshop Elements.