The HomePod allows you to play music from your Apple Music subscription or through AirPlay from another device. You set up the HomePod using an iOS device, and then can stream audio from a Mac, iPhone or iPad. You can also play music directly from the HomePod using voice commands and Siri. There are some preferences you can set in the Home app on your iOS device.
A new feature of Siri in iOS 11.2.5 is the ability to listen to short news podcasts with a simple command. You can use "play" or "tell" to trigger these podcasts even if you don't subscribe to them. You can also get business and sports news. This feature should come to the Mac soon, and is most likely being added now in preparation for the release of the HomePod.