I need help with my computer.

Look I know jack shit about computers so please explain this to me as simply as possible. Now, A few weeks ago my computer stopped working and I don’t know how to fix it. You see the power button light on the CPU is green and the monitor button light is yellow, but when I press the monitor button it won’t turn green. I remember this happened once before when the CPU was tilted slightly, but I just unplugged it and plugged it back in then it worked. So please help, also tell me if this should be in /r/.