Royal Holdem is basically regular Texas Holdem played with a stripped deck. All low cards, from 2 to 9 are removed from the deck, so there’s only the Ts, Js, Qs, Ks and As left in it. That makes a total of 20 cards, which limits the number of players who can take part in the game to 6.
6x2=12 + 3 burn cards = 15 + 5 cards on the flop, turn and river, respectively = 20.
The strategy applicable for this game is different from basic Holdem strategy, not only in light of the fact that Royal Holdem is a lot more likely to be played short-handed, but also because you obviously won’t have to wait around hand after hand for some high cards to hit you.
As a matter of fact, in Royal Holdem 10s and Js will be the low cards, and K and A the high ones.