Speech recognition is using your voice to control the computer and to insert text.
For speech recognition within Word, Outlook, and PowerPoint, buy an Office 365 subscription, which includes Dictation. If you're already an Office 365 subscriber, make sure you have the latest version of Office.
If you are an Office 365 subscriber please see Dictate with your voice in Office. Customers who are not Office 365 subscribers, can use Windows Speech Recognition.
To set up Windows Speech Recognition, go to the instructions for your version of Windows:
Are you looking for Text-to-speech? See Use the Speak text-to-speech feature to read text aloud. Excel has text-to-speech functionality built in to the program. To use text-to-speech commands in Excel, see Converting text to speech in Excel.
On the Mac, within your Office application, select Edit > Start Dictation. (Or tap the fn key twice)