iCloud is how we move documents, pictures, videos, and other data back and forth between iDevice and computer.

iCloud is storage in the 'cloud' (="don't worry about it, it's somewhere out there in the interwebs"), managed by Apple. iDevices can natively use the iCloud for storage, as long as they have access to the internet via wifi or the 3G data network. PCs or Mac computers can also access the iCloud, to pick up or deliver data files. The iPad 'Office' apps (Pages, Numbers, Keynote) can read and write to Microsoft Office files. This facilitates file sharing between iDevice and computer.

As of 2011.10.12, Apple is providing 5GB free storage in iCloud, along with iCloud features like "Find My iPad", and remote iDevice wiping (for clearing personal data in case your iDevice is stolen or lost).