Alexa is Amazon's voice AI that is associated with their Echo smart speaker. It can respond to vocal commands and mimic conversations through Amazon's cloud-based service, Alexa Voice Service (AVS). With Alexa, you can control various tasks in your home, such as creating shopping lists, setting reminders, and even controlling appliances like a towel warmer. It can also be integrated with other compatible smart home devices, making it a central part of a full smart home setup.