Default [Q] newbie with questions

What does "bricked kernel" mean? I have a HTC one, rooted.
It is a european model which I believe is called M7?
When I google to get the kitkat 4.4, I get too many different solutions Need some advice on what to download since I have no idea which one of them that is good.
It's been some time since I used the phone, but back then I rooted it and did a "s-off or on"-thing.
Downloaded and installed some "pacman"-theme ROM that was ok.
But I want to delete this now and update to 4.4 kitkat, but want to keep the phone rooted.
Anyone that can link to a "step-by-step" guide on how to do this?
I downloaded a rom called Smasher X 5.1
Is this rom "based" on the kitkat 4.4?