These are the highest rank of hands, Royal flush followed by a straight flush. If there are two straight flushes the player with the highest card will win.
Four of a kind is next. Like with flushed, if there are two four of kinds, the highest will win. Four of kind kings will beat four of kind queens.
Straights are next in the ranks of hands. If there are two straights, the player with the highest card will win.
When dealt your hand try to hold, if possible, when you have hands that will lead to these outcomes.