The iCloud.com portal communicates directly with any of your connected Apple devices – iPhone, iPad or Mac. When you type a query, this device performs the search locally and returns the results to the browser. Concretely, Apple has set up a private and secure search engine. No index of your content is stored on Apple’s side.
Search works in two sections of the icloud.com site: iCloud Drive and Photos. In iCloud Drive, you can search by file name, folder name, or document type. In Photos, the query concerns dates, identified people and geographic locations. Apple says no history will be kept on its servers, with the option to export a CSV file of the last 28 days of activity or delete it from the device.