It could be said that the function of Dictation is exactly the opposite of a voice synthesizer. It is a voice recognizer that lets you dictate to the program using a microphone and it will write what you`re saying.
This way, with Dictation you can be very productive. You can make a series of recordings, which are saved in WAV format, and later this WAV sound file is automatically converted into text. Dictation comes equipped with a vast dictionary of terms, which can be increased by the user if they wish.
Logically, to be able to use Dictation you need a sound card and a microphone.