iCloud: Keep photos up to date across devices with iCloud
You can set up iCloud Photos on your iOS devices, your Mac, your Apple TV, and your Windows computer. If you add or edit photos and videos on an iOS device or a Mac, the changes appear on all your devices where iCloud Photos is turned on, and you’re signed in with the same Apple ID.
When you set up iCloud, you get 5 GB of free storage space, which is used for iCloud Photos (as well as your other iCloud storage needs). As your photo library grows, you can upgrade your storage space as needed.
See the Apple Support article System requirements for iCloud.
Photos and videos are uploaded to iCloud Photos when your iOS device, Mac, or Windows computer is connected using Wi-Fi or Ethernet. Photos and videos are also uploaded from your iOS device when connected to a cellular network. For best results, also use Wi-Fi or Ethernet (with a broadband Internet connection) to download your photos and videos from iCloud Photos.