In my eyes, a premium is most likely a short single English word .com. These have all been taken, so there are none left. However there are emerging ngtlds where you can still buy these premium words - it's a gamble though, but one I have taken myself.
There are some exceptions to the above, like a truly great two worder or some emerging tech that you manage to get the .com before anyone else etc.
My advice is don't focus on these unobtainable premiums, unless you come here with a large budget. Focus on a niche, research and get a few good two word domains. Domains that make sense and have a good search volume.