Hello The Countess,
Based on your post it seems you would like more information about iCloud and photo management. Syncing photos your computer and removing them from your iPhone is great way to free up storage space. Photos are still kept in your Photo Stream for some time, which do take up your iCloud storage. I have linked to an article which provides more information:
iCloud: My Photo Stream overview
With My Photo Stream, the photos you take with your iOS devices or import to your computers appear automatically on all of your devices. It’s a great way to get all your latest shots on all your personal devices.
How it works
You can take a photo with your iOS device, or import photos from your digital camera to your iPad or your Mac or Windows computer. iCloud automatically pushes copies of the photos over any available Wi-Fi or Ethernet connection to your other devices.
The photos appear in My Photo Stream on these devices:
On your Mac, in iPhoto or Aperture
On your iOS 7 device, in the Photos app
On your iOS 8 device, in the Photos app (when iCloud Photo Library beta is not turned on)
On your Apple TV, under iCloud Photos
On your Windows computer, in the Pictures Library
On your iOS 8.1 device (when iCloud Photo Library beta is turned on), your most recent photos are uploaded to iCloud and appear in All Photos in the Photos app.
Note: When iCloud Photo Library beta and My Photo Stream are enabled on your iOS 8.1 device, your recent photos will upload to My Photo Stream but new photos from devices without iCloud Photo Library beta will not be imported.
To conserve storage space, My Photo Stream keeps only your latest 1000 photos on your iPhone, iPad, or iPod touch. On your Mac and Windows computers, every picture from your photo stream can be automatically downloaded and kept permanently.
You can also set up your Mac and Windows computers so your new photos appear in a My Photo Stream album. Your computer has more storage than your iOS device and can automatically import all photos from My Photo Stream to your photo library.
If you take photos with burst mode or image stabilization, only the photos you select as favorites when using burst mode, and the final composite image shot with image stabilization, are added to My Photo Stream. If you want all burst-mode photos uploaded to My Photo Stream and your iPhone has iOS 7.1 or later, go to Settings > iCloud > Photos (or Settings > Photos & Camera), then turn on Upload Burst Photos.
Note: To prevent unintended or excessive use, My Photo Stream limits the number of photos and videos that can be uploaded within a given hour, day, or month. For more information, see the Apple Support article
My Photo Stream and iCloud Photo Sharing Limits.
You may also want to review this page for further resources:
iCloud - Photos - Apple Support
Thank you for contributing to Apple Support Communities.
Cheers,
Bobby_D