Let’s investigate all iCloud Photo Library features, that lets user to sync all photos and videos to iCloud, so that user will have the access to them from any device. It features to keep optimized and lightweight versions of your entire library. This allows to save space on your device. The original resolution of your entire library is stored in iCloud Photo Library. When you enable it the Camera Roll and My Photo Stream album will replaced with an All Photos album.
One of the limitations currently is that Albums are not synced to photo library. The files are stored in All Photos (which includes videos), Videos (which only has videos), and Favorites.

iCloud Photo Library is currently in its beta, so please proceed with caution. To turn on library need:
- Go to Settings > iCloud > Photos & Camera.
- Then click on the on/off toggle for iCloud Photo Library (Beta) to enable it.
Important note, your device needs to be on iOS 8.1 or higher to enable iCloud Photo Library.
Currently, there is no native app available for iCloud Photo Library. So you can access the photos and videos in the All Photos album on your iOS device.
Apple company plans to release Photos app for Mac soon this year. But until that time you can access your photos and videos only on iCloud.com. You need to login to iCloud account on your iOS device, and to access the files, click on iCloud Photo Library.
How Upload Photos Manually Using iCloud Photo Library Features
Upload photos by going to iCloud.com on your Windows PC or Mac running OS X Mavericks or earlier. Sign in to iCloud.com using your Apple ID, then tap on Photos, followed by the Upload button at the top. Select the photos you want to upload and tap OK.
Note: iCloud library supports the following photo and video formats: JPEG, RAW, PNG, GIF, TIFF, and MP4.
To prevent your photos from being synced to other devices you can go to Settings > iCloud > Photos and disable Upload to My Photo Stream.
The entire library does get counted against your iCloud storage. iCloud storage is used for iCloud Backup, iCloud Drive, iCloud Photo Library beta, iCloud Mail, and data from apps that use iCloud. Although, purchased apps, books, music, TV shows, movies, My Photo Stream do not get counted against your iCloud storage.

If your iCloud storage limit will be exceed, new photos and videos won’t be uploaded to iCloud, so they won’t be available on your other devices. You will need to upgrade your storage plan or reduce the storage you’re using.
To save space on your iOS device you need to go to Settings > Photos & Cameras > iCloud Photo Library or Settings > iCloud > Photos and select Optimize iPhone Storage.
When you edit a picture, the changes are updated across all your devices. If you’ve selected Optimize iPhone/iPad Storage then it will download the original photo or video for editing. The original pictures are stored in iCloud so you can revert back the changes at any time. If you delete a photo or video from the Photo app, it also gets deleted from iCloud Photo Library.
Although, you have the option to recover the photo from Recently Deleted album for 30 days. A little useful fact is that photos are backed up on Apple servers for 30 days after they’re deleted from your device. These are all useful iCloud Photo Library features you need to know.