What is theos?
A cross-platform suite of tools for building and deploying software for iOS and other platforms. (wiki)
What can I do with it?
You ever thought about how developers create cydia tweaks/apps? They do so using theos. If you want to get into developing for iOS and learn more on how apps/tweaks work, you can start off by using theos on your jailbroken iDevice. It is also possible to install it on Mac and Windows and Linux based OS, but this tutorial only covers iOS.
Guide:
[hide] https://www.iosmods.com/downloads/theos.pdf [/hide]