Cortana is a virtual assistant developed by Microsoft that uses artificial intelligence to help users perform tasks and find information. It was first introduced in 2013 and is designed to assist with various functions, such as setting reminders, answering questions, and managing schedules. Cortana is integrated into the Windows operating system and can be accessed through voice commands or text input. It aims to provide a personalized experience by learning from user interactions and preferences, making it a valuable tool for productivity and organization.