How to Use Dictation in Mavericks OS X
The new Mac operating system is making life simpler for you. In Mavericks, you can speak wherever you might otherwise type, be it inside TextEdit or in numerous other apps.
To turn on this Dictation feature, press the function (fn) key on your keyboard twice or choose Edit→Start Dictation. Dictation isn’t always perfect, but in a relatively noise-free environment, it should do just fine. Especially, if you are pressed for time, or attempting to multitask (whether successfully, or unsuccessfully). And make sure your Mac has an appropriate microphone or other input device.
When you dictate, your words are recorded and sent to Apple, where everything gets converted to text (ideally, with minimal errors). But other information is also sent to Apple, including your first name, nickname, and contacts.
The idea is to help Apple understand what you meant to say, thus improving the accuracy. If you find this arrangement troubling, you can turn off Dictation. In System Preferences, click Dictation & Speech; then click Off in the Dictation section. Apple deletes your user data and any recent stuff that you recorded.
You can also restrict access to Dictation in parental controls.