iCloud is a cloud storage and cloud computing service from Apple that allows users to store data such as documents, photos, and music online. It provides seamless synchronization across all Apple devices, ensuring that users can access their files from anywhere with an internet connection. In addition to storage, iCloud offers features like iCloud Drive, iCloud Photos, and iCloud Backup, which help users manage their data efficiently. With iCloud, users can also share files and collaborate with others, making it a versatile tool for both personal and professional use.