As in Deuce to Seven Triple Draw, you are trying to make a low hand, but in Ace to Five straights and flushes do not count against you and Aces play for low. This means that the best possible hand you can have is A2345 with flushes being irrelevant to the rank of the hand. In Ace to Five, A2345 is called a wheel. A2346 is the next best hand and is called Number 2 or a 6-4. The next best hand is A2356 and so on. 23456 is the worst possible 6-low and the fact that it is a straight does not count against you.
Other than the hand rankings, the game play is identical to deuce to seven.