iCloud is Apples cloud storage service, offering integrated online backup and syncing for Apple devices. iCloud is built-in on iPhones, iPads, and Macs, but can also be accessed on Windows. While other services allow you to upload any type of file, Apple chooses to place your data into different compartments. This can be confusing for example, iCloud will store your documents forever, but will delete your stored photos eventually. What iCloud Syncs and Backs Up iCloud is an online service linked to your Apple ID. When you set up a new iPad or iPhone, iCloud is enabled by default. Apple provides a free 5 GB of iCloud space to each account, which is used to store the following things online: Mail: You can choose to use an @icloud.com email address on your device. If you do, iCloud will store your mail and it will also be accessible on icloud.com.