Apple has made it that anytime you turn on iCloud Photo Library, and every photo you take will automatically upload itself in full resolution. And also, when you edit any of your photos it will also automatically update everywhere.

Therefore With iCloud Photo Library, you will save space by replacing photos on your device with smaller versions. The iCloud photo will help you to save unlimited photos in its library.

This is basically for Apple product users such as iPhone users.
Read more:http://www.viralvista.net/how-to-download-photos-from-icloud-using-pc/