An official at-bat comes when a batter reaches base via a fielder's choice, hit or an error (not including catcher's interference) or when a batter is put out on a non-sacrifice. (Whereas a plate appearance refers to each completed turn batting, regardless of the result.)
At-bats are used as the denominator when determining batting average and slugging percentage. Players who bat higher in the order will typically finish the season with more at-bats than players who hit toward the bottom. Similarly, players who walk infrequently also typically record a higher-than-usual number of at-bats in a season, because walks do not count as at-bats.
In A Call
"times at bat," "turns at bat"