By default, Google photos are private and not public. Only you can access your photos. The videos and photos you store on Google photos are visible to only you. Unless you choose to share your photos with friends and family. You can choose to use public URL on your photo so your photo can become public.
The default position is supposed to be private. Google photos are actually public once you share them, even if that's only with one person. Photos on Google Drive are private assuming you set your privacy settings so that only the people you want can see your photos.
Think of Google photos like taking a picture on a bus or standing on the stage and showing them to a friend, but so that anyone in the bus or audience can see them: that's Google photos. So, don't expect them to be private. If this is important use Google Drive and go into your settings, taking care not to rush your options.