A rule that when one player commits a foul or scratch, his opponent can place the cueball anywhere on the table, and start shooting from that point.
After a foul the freedom to place the cue ball anywhere on the table or behind the head string. Check the World Standardized Rules for the game specific ball in hand rules.
In certain games, a player may have Ball in Hand after a foul by his opponent. The player may place the cueball anywhere on the table.