Siri is a virtual assistant and can be used to control certain functions on the phone using voice commands.
If Siri wasn’t activated while setting up your iPhone, you can activate it by opening Settings, pressing Siri & Search and then turning it on. You’ll want to ensure Press Home/Side Button for Siri is toggled on.
To access Siri, press and hold the Side button (or Home button if your device has one) for a few seconds until the Siri icon appears at the bottom of your device’s screen. When you see the Siri animation appear on screen, you can ask Siri a question or issue a command.
Or, if you have it set up, you can simply say the phrase “Hey Siri” to get its attention and then speak your request.
Note that on older versions of iOS, the Siri interface would cover the whole screen – but from iOS 14 onwards, the overlay takes up much less space.