First introduced in Windows Phone 8.1, Cortana is a personal assistant capable of automatically organizing your life, acting on your issued commands, performing requested research, and learning how you work and play and adjusting to fit your needs – becoming even more useful over time.
Now included with Windows 10, Cortana works across all your devices, including PC, tablet, and phone. Additionally, depending on the device you are using, Cortana adapts. For phones, Cortana interaction is brief, but when on a Windows 10 tablet or PC Cortana is a productivity maven, and can deliver rich, valuable information whenever you call her name.
Cortana is not turned on by default in Windows 10, so you'll need to enable the functionality.
To turn Cortana on in Windows 10:
On your Windows 10 PC or tablet, go to the search box—it’s in the Windows Taskbar, just to the right of the new Start button.
When prompted to get started with Cortana, select I’m in.
When prompted to let Microsoft use your info, select I agree.
When prompted to turn on speech, inking, and typing personalization, select Yes.
When Cortana asks what she should call you, enter your name or nickname, and then select Use that.