Echo devices are designed to detect only your chosen wake word (Amazon, Alexa, Computer, or Echo). The device detects wake word by identifying acoustic patterns that match the wake word. Once the word is detected, audio begins streaming to the cloud, including a fraction of a second of audio before the wake word. No audio is stored or sent to the cloud unless the device detects the wake word (or Alexa is activated by pressing a button).
Skills are voice-driven Alexa capabilities. You can view and enable skills in your Alexa app and enable certain skills by voice. You can use a skill by saying a specific phrase,
called Amazon, Alexa, alexa.amazon.com, Echo etc. When you use a skill, it may exchange related information of that skill, such as your answers when you play a trivia skill, your ZIP code when you ask for the weather or the content of your requests.