Royal Flush is a term used in poker that talks about the best possible hand players can get if no wild cards are being used or if, let’s say, you are not playing low poker.
The hand is comprised of a 10, Jack, Queen, King, and Ace, all of which have to be of the same suit. Think of it as a combination of a Straight and Flush comprised by the highest-ranking cards.
If you are playing Texas Hold’em poker, for example, one of the most popular variations of poker, and you land a Royal Flush, you are guaranteed to win the hand since landing two Royal Flushes during a single hand is impossible — you need at least three community cards and two hole cards to get it, which leaves everyone else with only two community cards to work with.
However, landing even one takes a lot of luck since the odds of landing a Royal Flush are 1 in 30940.