Cortana is the first personal digital assistant which is a patented product of Microsoft. She is available on all the devices running Windows 10 and iOS devices. Cortana maintains the same user interface and functionalities as it has in Windows devices. Some features are kept to the native environment as of now, for example, toggling settings, opening apps or activating Cortana “Hey Cortana” are only available on Windows for now. We shall hope to see final release in the coming weeks overpowering the beta release.
Source: https://thehackernews.com/2015/08/cortana-for-android.html