Photos

When icloud photo library is set up https://support.apple.com/en-in/HT204264

• And photos are synced with iCloud server - On your Mac with OS X 10.10.3 or later, go to System Preferences > iCloud. Click Options next to Photos, then select iCloud Photos.

And photo preferences are correctly set up https://support.apple.com/en-in/guide/photos/pht5156cc968/4.0/mac/10.14

The photos can be selected from photo application of the Mac https://support.apple.com/en-in/guide/photos/pht40b0be510/4.0/mac/10.14

https://support.apple.com/en-in/guide/photos/pht6e593112/mac

and deleted https://support.apple.com/en-in/guide/photos/pht3bfab2f96/mac

The same photos will get deleted from the iCloud server ( it will start acting as a mirror ) .

To reduce the iCloud storage data see some articles https://support.apple.com/kb/PH12790?locale=en_US

https://support.apple.com/en-in/HT204247

https://support.apple.com/en-gb/guide/system-information/sysp4ee93ca4/mac

https://support.apple.com/en-in/HT206996

If I put my Photos to Icloud

That will depend on how you are doing it. If you are using the Photos.app and iCloud Photos Library, your Photos Library will sync with iCloud. Any photo you delete in Photos on your Mac will be deleted from iCloud as well and all other devices syncing with iCloud. When you are using iCloud Photos Library with Photos.app, do not delete any photo you want to keep. Just enable "Photos > Preferences > Optimize Storage" and Photos will remove the high resolution versions of photos from your Mac and just keep smaller versions for browsing, if your Mac is low on storage. You will then need to have an internet connection to use your photos in the Photos.app. With "optimize Storage" the library can be reduced to 20% to 20% of its original size.

If you are not using the Photos.app and your photos are just in folders in the Finder, not in a Photos Library, you can use the web interface to iCloud to upload photos into the cloud. Open www.icloud.com, sign into the Photos.app there, and use the upload button to upload photos. Then you can make a backup copy of the photos you uploaded on an external drive and delete the versions from your Mac. But you will be limited to the web interface to browse your photos. It is very limited and not as versatile as the Photos.app on your Mac.

You're welcome 😊