You can go through our guide on how to install Steam on Chromebook for detailed information.
I have played CS: GO and Deceit on my Chromebook from Steam and the gameplay has been decent, at best. As for how we are able to install Steam and run PC games on Chromebook, well, we are installing the Linux version of Steam and enabling a compatibility layer called Proton (a modified version of Wine) to play AAA titles on Chromebooks.
