With Dictation, you can use your voice instead of typing text.
Use these steps to start dictating:
Click the window where you want to start typing.
Press the fn (Function) key twice, or choose Edit > Start Dictation.
Dictate (speak) what you want your Mac to type.
When finished, click Done or press the fn key again. Your spoken words then appear in the text field.
To getting started with Dictation or to learn about advanced features of it, visit this page on Apple's site.