Siri

Siri lets you use your voice to send messages, schedule meetings, place phone calls, and more.

INSTRUCTIONS & INFO

Siri is the intelligent personal assistant that helps you get things done just by asking. It allows you to use your voice to send messages, schedule meetings, place phone calls, and more. But Siri isn't like traditional voice-recognition software that requires you to remember keywords and speak specific commands. Siri understands your natural speech, and it asks you questions if it needs more information to complete a task.
To ask Siri something, hold down the Home button until you hear two quick beeps and see "Go ahead, I'm listening..." on the screen.
Note: You can also press and hold the Home button and release it when you're done speaking.
If you're using iOS 8 or later, you can ask Siri a question starting with "Hey Siri." without having to hold down the Home button.
Note: You'll need to turn on Hey Siri first by going to Settings > General > Siri > Allow 'Hey Siri.'
What types of things can I ask Siri about or ask it to do? You can ask Siri to make a call, find a business and get directions, schedule reminders and meetings, search the web, identify songs with Shazam, and more. You can even ask Siri "What can you do for me? or tap the "?" in the left corner of the screen when you bring Siri up. You'll see examples of things Siri can do, along with ways you can ask for things.
The audio wave moves across your screen, letting you know Siri is listening and processing your request. After you've started a dialogue with Siri, tap the Microphone icon to talk to it again.
To change how Siri sounds: Change the gender at Settings > General > Siri > Voice Gender. The voice genders that are available vary by country and region.Change the language at Settings > General > Siri > Language.
Note: Your iOS device initially uses a compact voice for Siri. Your device will automatically download and install a more natural-sounding voice when you first connect to power and a Wi-Fi network.
How does Siri learn who I am? If Siri knows who you are, it can use your information to better help you. To make sure Siri knows who you are, select your contact information in Settings > General > Siri > My Info. Your information is used for questions like 'How do I get home?' or 'What good restaurants are near work?'
Note: Learn more from Apple support article: About Siri