mk II or mk III?

Im relatively new so, this may be a dumb question.  What gives with al the mk II & mk III stuff.  I see it various brands & an equally varied type of things.  Turntables, my new phono preamp & cartridges.  I’m pretty sure I saw an amp & some speakers Both for sale here.

I’ve googled & did a thread search here. I can’t find anything that makes something an “mk” let alone a II or III.

Unless... My Kryptonite?? Some of the stuff I see makes me weak in the knees, my head spins & I drool profusely.

I’m really curious.  Thanks for sharing your knowledge.