Whats wrong with my mac screen

Hi everyone i hope you can help me

I switched on my white imac today and the screen had spilt in two one side had my desktop and the other had 2 black and one white vertical stripe,what has gone wrong and is it expensive repair,i think i have loaded a photo

I have done some research and could it be the inverter,i know it's an old mac but i'm attached to it now

I would reset the NVram first

Restart while holding down command-option-PR and wait for the mac to restart a couple of times, then let it boot

Thanks louishen i forgot to mention that i did a screen shot as previously mention in another thread and there was no lines on the screen shot would this mean that it could possibly be the screen or inverter.

Can't do a NVram reset just yet as it's not my machine.

thanks again

I would guess its either the display or the logic board. You might be able to replace the screen for not too much, but if it's the logic board it's going to be somewhat expensive.