Samsung’s Bixby assistant on the brand new S8 and S8 Plus does not work with voice commands yet. The service will be fixed with an update in the near future. Samsung is expected to have this fixed soon. It makes the S8 less of a top of the line phone without it. The S7 Edge is basically the same phone with a few downgrades until the Bixby assistant is ready. Surprisingly though the Samsung vision is working.
Bixby is an assistant like Google Assistant or Siri but it has a feature called Bixby Vision which allows you to take a picture of something and it can tell you more about the item. It can also give you sites to buy it at. This feature is ready and works well.
If you would like to use a voice assistant, you still have Google Now. To activate it, just hold the home button down until a white border starts to appear on the phone then you can talk to it and set up “OK Google”. OK Google is a feature that allows you to say “OK google” with your phone display off and then start talking and it will respond.