https://arstechnica.com/gadgets/2017/11/amazon-echo-and-alexa-products-comparison/

Amazon debuted the original Echo a few years ago, and it raised eyebrows in the tech industry. The Echo is a smart home speaker that houses Amazon's Alexa virtual assistant, an AI helper that helps you complete daily tasks using only your voice. Since its debut, users of all levels of tech prowess have embraced Echo and Alexa, finding practicality in a voice-controlled assistant and all the things it can do.

Both Alexa and the Echo have evolved since then to meet the needs of an ever-growing market. After the Echo and Alexa came Google Home with the Google Assistant, the Harman Kardon Invoke with Microsoft's Cortana, and the forthcoming Homepod with Apple's Siri. Amazon has an advantage over all these competitors because it has had the time to develop many different Echo devices and expand Alexa to be a multifaceted assistant, thanks to third-party integrations and skills. ("Skills" is Amazon's word for apps, in this case.)