You start a conversation with Alexa using an invocation name, or wake word. The default wake word is Alexa. These days, you can also use the wake words Echo, Computer, and Amazon. You can set the wake word from the Amazon Alexa app, which you can download from the Apple App Store or Google Play Store.

Once you activate Alexa, you can invoke a skill published by Amazon, or launch a custom skill published by other developers, using an invocation name. You can launch your own skills from your Echo devices without needing to publish them, as long as the device is linked to the same Amazon account as your developer portal.

Your Alexa skill can define different intents. Intents can be considered as different functionalities provided by your skill, such as welcoming someone to the app, responding to a question, taking an action, and so on. After you launch a skill, you need to say a phrase, and each phrase will be mapped to an intent.

For example, consider the sentence Alexa, open Cloudericks and please say the intro. Alexa is the wake work here, Cloudericks is our invocation name, and please say the intro is the utterance. The utterance will invoke an intent that performs the actual introduction. The intent can be defined within an AWS lambda or an external API.

You usually define more utterances for an intent, such as please say intro, please say the intro, say intro, and so on. You can define more utterances to make your application more flexible and then improve it further from the analytics data for failed utterances. 

Instead of saying open Cloudericks to launch the skill, you can also use the invocation name in your sentence. For example, instead of saying Alexa, open Cloudericks and please say the intro, you can say Alexa, please say intro for Cloudericks, as we did in this recipe.