In the Settings app under Settings >Photos>... there are a few options for saving/keeping photos that you take, among other options, such as screen shots, or pictures that you save from websites, and have those saved to the cloud (iCloud) for syncing/sharing to any device associated with your Apple ID. They (the iCloud options) need to be toggled on to activate them - if you choose to turn these cloud options on, then the current photos/pictures in your camera roll on that device will be synced to iCloud, and will be accessible from any of your linked devices by selecting the iCloud album on those devices. Keep in mind that Apple only provides 5GB of free storage space in iCloud so you may (probably) will fill up that space pretty quickly if you have a lot of pictures/videos synced.