You can use Siri on an iPhone XR, iPhone XS, or iPhone X in two ways: either with the Side button, or through a "Hey Siri" voice command.
The Announce Calls feature on iPhone was introduced with iOS 10, and when enabled Siri will "speak" the name of the contact calling you.
The familiar orb at the bottom of your screen is now a thing of the past. Update your iPhone to get a glowing, colorful border when you summon Siri.