My PC has just stopped working

I was using my PC last night, came downstairs this morning to switch it on and nothing. The monitor light comes on but there is nothing from the tower, no fan, no lights. I have checked the power socket and that’s fine. I had a new motherboard fitted about 18 months ago but it can’t be that surely, as the monitor light comes on indicating that there is power to it from somewhere. If you have any advice for me please tell me in simple terms because I am not PC literate at all.