There are two ways of using the ace in Texas holdem because it can either be used at the start of a sequence or at the end of it. Given that the poker hand rank called a "straight" covers all five-card unsuited poker hands in consecutive order, this hand rank is the only place where the ace can have the lowest single position in holdem. Otherwise, it holds the highest value for a single card in the game. So what are the two ways of using the ace in a Texas holdem straight?
The first way is when it's used at the end of the sequence in what's called "Broadway" in poker lingo. This is made up of an unsuited ten, jack, queen, king, and ace. And given the nature of this hand rank, Broadway is the best or supreme straight because it uses the ace as its high card, as it's generally known to be, in the five-card sequence.
The second way of using the ace in a Texas holdem straight is called a "wheel" or "bicycle" in poker lingo. This is the lowest or worst series of consecutive cards in the game that includes an ace, two, three, four and five. Given this sequence, the ace is the lowest card in the order having a value of one while the high card in this rank holds the value of five.
Generally, the 13 single cards in holdem are ranked from lowest to highest from two to ten then jack, queen, king and ace. And since a straight is not limited from starting only at a six-high combination (two to six unsuited), the ace automatically holds the value of one when combined with unsuited cards valued from two to five in that order. This, in turn, makes a five-high straight that's possible in Texas holdem.
By its very nature, a Texas holdem straight is defined as a five-card poker hand in consecutive order from lowest to highest. This includes using the ace to have the lowest value that's unique in this poker hand rank. In effect, the wheel or bicycle (ace to five, unsuited) is the lowest and worst sequence possible in this hand rank. Broadway (ten to ace, unsuited) is the highest in this hand rank of unsuited cards. And given those two ends of a Texas holdem straight, the in-between sequences include five-card poker hand series making the six-high, seven-high, eight-high, nine-high, ten-high, jack-high, queen-high and king-high straights in the game.