What is that? It beats a King? Then I've been playing without knowing all the rules.
A suited Queen-Jack is just a starting hand, it can’t beat a King high on its own, but in Hold Em, you use your starting hand to complete a full five card hand with the other common cards that are dealt.
When you look at all the possible hands that could be made with a starting hand, you can then compare them to each other and get a ranking of the best starting hands. That just gives you an approximate idea of how likely each starting hand is to make a very good, possibly winning hand, but it’s the best information that you have to go with when making that first bet in Hold Em, since you haven’t seen any of the common cards yet.
So, based on starting hand rankings, Queen-Jack suited is a pretty good starting hand, because a lot of good, probably winning, hands can be made with it. I don’t have all the rankings memorized anymore, but I’m pretty sure that QJ suited is higher than King + any card less than 9 unsuited.
The key is in the possibilities that can be made with both hands. QJ has the advantages of: being suited, creating flush possibilities, being two face cards, offering two different winning pair/trip/quad/full house possibilities , and being two cards than can be used to complete a straight, and a high straight at that, possibly a high straight flush. Also, when you rank cards that can form straights, two consecutive cards like QJ can form more kinds of straights than cards with one gap, two gaps, or three gaps between them.