Using Google Drive app
I wanted to upload some iPhone photos to the Google Photos section of my Google Drive. I opened up the Drive app and went into Google Photos. The screen says "Your Google Photos will appear here." I clicked on the blue plus sign and chose Upload, then Photos and Videos. Then I chose All Photos (which doesn't really show all my photos for some reason) and selected 15 of my iPhone photos, and tapped Upload. It uploaded them, but into the regular My Drive section of Google Drive rather than Google Photos. What gives here? Maybe I'm misunderstanding what Google Photos is.
iPhone 5s, iOS 9.3.1