One-and-one is a bonus free throw awarded for non-shooting fouls.
This only happens when the team who incurred the foul exceeds the initial foul limit. This bonus is usually given in amateur leagues like high school and college basketball games.
The NBA does not have this rule. Instead, the NBA enforces that on a player’s fifth foul on a player, the opposing player will get two shots.
In the NCAA, players of the opposing team receive a one-and-one if the other team has made seven fouls in a half.