Apple's Siri is a virtual assistant developed by Apple Inc. that uses voice recognition technology to perform tasks and answer questions. It can help users send messages, set reminders, play music, and provide information about the weather or news. Siri is available on various Apple devices, including the iPhone, iPad, Mac, and Apple Watch. Siri operates by interpreting spoken commands and responding with relevant information or actions. It utilizes machine learning and natural language processing to improve its understanding of user requests over time. Users can activate Siri by saying "Hey Siri" or pressing a button on their device.