Definition of royal flush
A "royal flush" is a royal flush! This is the strongest poker hand there is. There are 4 types of royal flush's: T-J-Q-K-A all hearts, spades, diamonds or clubs. This hand is extremely rare and that's why it's so strong. The rarer the poker hand, the stronger it is. Even with a hand like JT matching, you'll only flop 0.005% of the time a royal flush! No poker hand can beat a royal flush and the strongest hand to beat is the straight flush (e.g. 5-6-7-8-9 all in spades).
Royal flush and badbeat jackpot
If you are playing online and there is an badbeat jackpot on your table (progressive jackpot), you might be able to win that jackpot with your royal flush if you ever win against a straight flush or square. The majority of the time, an badbeat jackpot is won when a player loses with a minimum of 8-of-a-Kind with two cards in hand (in this case, with 88 in hand). If you win the hand with your royal flush (always considering your two hidden cards), you would get 25% of the progressive jackpot (the loser of the hand would receive 50% of the badbeat for losing with such a strong hand).