The royal flush is a case of the straight flush. It can be formed 4 ways (one for each suit), giving it a probability of 0.000154% and odds of 649,739 : 1.
Five-card draw (also known as Cantrell draw) is a poker variant that is considered the simplest variant of poker, and is the basis for video poker. As a result, it is often the first variant learned by new players. It is commonly played in home games but rarely played in casino and tournament play.