Effective Use of ICloud Storage

Note: If you delete Photos and Videos on your iPhone it will deleted on iCloud too. With Optimize Storage, smaller, space-saving photos and videos are kept on your device.

Store your photos and videos in iCloud

Your photos and videos are stored on your device in their original, high-resolution version. This means that they use a lot of space on your iPhone, iPad, and iPod touch. With iCloud Photos, you can make more space available on your device and have your entire collection, everywhere you go.

Get started with iCloud Photos:

1. Tap Settings > [your name] > iCloud > Photos.
2. Turn on iCloud Photos.
3. Select Optimize iPhone Storage to save space on your device.
4. 

With Optimize Storage, smaller, space-saving photos and videos are kept on your device while all of your original, full-resolution versions are stored in iCloud. And as long as you have enough space in iCloud, you can store as many photos and videos as you want.

You can got through the Manage storage suggestions on your iPhone which will do things like keep full-sized photos in iCloud but lower resolution ones on iPhone, etc. iCloud is used primarily for syncing, not storage. You would be better off using Dropbox or something similar if you want to use it as alternate storage.