iCloud is a cloud storage and cloud computing service provided by Apple Inc. It allows users to store data, such as documents, photos, and music, on remote servers for download to iOS, macOS, or Windows devices, to share and send data to other users, and to manage their Apple devices if lost or stolen. It also provides the means to wirelessly back up iOS devices directly to iCloud, instead of being reliant on manual backups to a host Mac or Windows computer using iTunes.

iCloud’s features include:

1. iCloud Drive: This feature allows users to store any kind of file and access it from any device.
2. Photo Library: iCloud Photo Library automatically stores all photos and videos in iCloud, making them accessible from any iOS device or computer.
3. iCloud Backup: This feature backs up an iOS device to iCloud, allowing users to restore the device to a specific point in time.
4. Find My iPhone (or Find My): This feature helps locate lost or stolen Apple devices, including iPhones, iPads, Macs, and AirPods.
5. Keychain: iCloud Keychain securely stores users’ passwords and credit card information.
6. iCloud Mail: A free email service from Apple with ample storage, integration with other Apple services, and a simple, user-friendly interface.

iCloud offers a limited amount of free storage, with options to purchase additional storage if needed. It’s deeply integrated into Apple’s ecosystem, providing seamless synchronization of data and settings across various Apple devices.