Poker sequence refers to the ordering of the cards. For example, five consecutive cards in sequential poker rank order make a straight in poker. Thus, if you hold consecutive ranks, i.e., 6,7,8,9, 10, you can refer to them as being in sequential order.
There are 52 cards in the pack, and the ranking of the individual cards, from high to low, is ace, king, queen, jack, 10, 9, 8, 7, 6, 5, 4, 3, 2. There is no ranking between the suits - so for example the king of hearts and the king of spades are equal. A poker hand consists of five cards.