Cunards Grills - Another name for first and second class?

I recently wrote a post about all the different benefits you can enjoy when you book a Princess or Queens Grill onboard a Cunard ship, (if you're interested you can read the post by clicking here). Ever since I wrote it though it's been praying on my mind a little. Are the Cunard Grills just a higher grade of cabin, as available on all other cruises lines or are they a sneaky form class system ie first, second and steerage?