Chrome Remote Desktop is a handy app that allows you to control a PC remotely from your Android phone.
Whether you're using it to access your PC or to take a look at a friend's or colleague's computer, Chrome Remote Desktop will hook you up. You simply need to install the Chrome extension on your PC then configure a PIN number to access from your phone.
The app works well enough, though it's a bit laggy at times. From a phone, control can be fiddly but on a tablet it's a great experience.