Parsec is an Android app that can stream loads of PC games to your Android device. With this app, you can join other user's ongoing games, as well as connect your Android device to your own PC (although you will need to install the Parsec windows program to do so).
Once you've created a Parsec user account, you can join any ongoing games, or get a group of friends together and play all kinds of PC games online, both cooperative and competitive. That being said, most of the games require a controller, so joining games is only recommended if you already have a controller connected to your Android device.
If you already own a PC with games, you simply need to download and run the Parsec program, and then you can convert your PC into a sort of server that you, and anyone you invite, can connect to and play awesome PC games.
Parsec is an app with truly great potential, that enables you to stream PC games to your Android device and play them anytime and anywhere (so long as you have an internet connection, that is).