Starting with watchOS 5, Apple has made several improvements to the Siri voice assistant.
Thanks to machine learning, Siri can now provide a wider range of contextual information. For example, it will be able to show your heart rate after a workout or the sports results of a match if your favorite team is playing.
You no longer need to activate everything using the phrase "Hey Siri" - just turn on the new wrist raise option, which automatically launches the voice assistant.
Also, if you're using AirPods Pro, you can ask Siri to activate the noise cancellation on your headphones, or find out the name of a track from your playlist.