If you just want to see, you can go to Settings-> iCloud-> Storage and Backup-> Storage Management.
On your Mac, you can go to " ~/Library/Mobile Documents
" and see what is stored in the cloud, including transaction logs (iCloud and master data) or documents (for example, Pages, Keynote). To be clear, it shows the contents of things on your iPhone / iPad that are shared with iCloud, not just Mac apps that use iCloud. You may need to enable iCloud on your Mac to see this folder.
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