https://goo.gl/NUem7h - Echo Dot is a hands-free, voice-controlled device that uses the same far-field voice recognition as Amazon Echo. Dot has a small built-in speaker—it can also connect to your speakers over Bluetooth or with the included audio cable. Dot connects to the Alexa Voice Service to play music, provide information, news, sports scores, weather, and more—instantly.
Echo Dot can hear you from across the room, even while music is playing. When you want to use Echo Dot, just say the wake word "Alexa" and Dot responds instantly. If you have more than one Echo or Echo Dot, Alexa responds intelligently from the Echo device you're closest to with ESP (Echo Spatial Perception).