Since attempting to install Steam and receiving the error message that there are apparently "held packages" on my system, I attempted to start my computer today and it repeatedly fails to load the OS. I also cannot boot to other media such as a CD/DVD or USB drive. I am stuck with a console interface of the operating system and I don't know how to get my main graphical interface back.
You messed up some dependencies by holding packages .
(I know that libstdc++ issue with steam and that there's a solution where you actually have to hold-mark certain packages, but you can definately fry your system with that. Also, you only have to delete a few library files in the steam folder to get it running, and if you ask a new quesion, I'm pleased to go more detailed about this.)
And you most likely uninstalled X and pantheon, the desktop environment of elementary OS. That way you will always see the command prompt when booting, since you deleted everything else. ;)