Final answer:
The message implies that the Freeform app data on an iPhone will synchronize with iCloud, making it available across multiple devices using the same iCloud account.
Step-by-step explanation:
When you receive the notification 'Freeform on this iPhone will be uploaded and merged with iCloud,' it means that the data associated with the Freeform app on your iPhone will be synchronized with your iCloud account. This allows for your Freeform data to be accessible across multiple devices that are logged in to the same iCloud account, ensuring seamless continuity of your work or projects within the app. The merging process involves uploading your Freeform content to iCloud and then combining it with any existing Freeform data stored in iCloud.