Between the two, Google Photos has an advantage because it offers apps for both Android and iOS—Apple Photos works best if all participants, sharer and sharee alike, have a Mac, iPhone, or iPad. Download the Google Photos app to any device, open it, and long-press on a photo to select that image. Tap on any other pictures you'd also like to share, then click the Share button, which looks like an upward arrow in the iOS app and a sideways V in the Android one. If your contacts also use Google Photos, you can add these pics to a shared folder that friends can view and add photos to. Alternatively, if they don't have Google accounts, you can email them a link that they can follow to view the shared photos in their web browsers.