The conjugate method is a system of weight training developed in the USSR and popularized by the Westside Barbell club in Columbus, Ohio. It aims to improve performance in one lift by use of special exercises.
If one uses more than 90% of their one rep max (1rm) year round, their progress will stall. One way around this limitation is to use similar, but different exercises. Special exercises for the bench press include incline bench press, close grip bench press, floor press. Special exercises for the squat and deadlift include good mornings, box squats, front squats, and rack pulls.
The conjugate method is typically used in a conjugated periodization plan.