Siri is a virtual voice assistant for Apple products that run iOS, watchOS, macOS and tvOS.
Siri uses voice queries to answer questions, make recommendations, and perform queries by integrating with multiple internet services, such as Wolfram Alpha, Yelp and Trip Advisor.
With continued operation, Siri will adapt to user searches, voice commands and usage preferences. Meaning that over time, results become more individualised.
Siri was originally developed by the SRI International Artificial Intelligence Center. Its speech recognition engine was provided by Nuance Communications, with advanced machine learning technologies to function.
Siri was first released for iOS as a standalone app in February 2010. Quick to spot its potential, it was purchased by Apple in April. It was then released as part of iOS in October 2011.
Since then, Siri support has been expanded over most of Apple's product range. Including the iPad, iWatch, Apple TV, HomePod and macOS itself.
With subsequent iOS releases, Apple is slowly adding further integrated features and (more importantly) opening up access to third party apps. This should allow users to interact with non-Apple services, such as being able to order a coffee, or make hotel reservations using installed apps.