One of the features of the PS4 is voice commands. Here's how to use the PS4 using voice commands:

You can use your voice to perform operations on the home screen and other areas. For voice input, use a headset (included) or the microphones on a PlayStation Camera.

Say "PlayStation". The microphone icon and the operations that can be performed next are displayed. The microphone icon lights up in blue during voice recognition.

Choose the operation you want to perform from the items that are displayed, and then say it.

If you don't say an operation within 10 seconds or if you operate the system with the controller, the voice recognition feature is disabled.
On the home screen, you can enable and disable the voice recognition feature with the L2 button on the controller.
Even if you are playing a game, you can say "PlayStation" and then say one of the following commands to perform operations:

Home Screen
Take Screenshot
Log In
To use the voice recognition feature, you must set a checkmark in (Settings) > [System] > [Operate PS4 with Voice].
If a headset and a PlayStation Camera are both connected to the system, only the headset's microphone is enabled.

Depending on the system language, English might be the only language available for voice input.
If there is too much ambient noise, your voice might not be recognized.