Pulling the shoulder blades back toward the spine, which is the finishing position of a row and the setup position of a bench press.
The rhomboids and middle trapezius do the work. Retraction gives the shoulder a stable base to press from and it is the difference between a row that trains the upper back and a row that trains the biceps.
On a bench press it happens before the bar moves: the client pulls the blades together and down, holds them there, and presses. That shortens the range slightly and gives the shoulder joint something solid behind it. Holding it under a heavy triple is a skill, and losing it near lockout is the most common cause of the shoulder discomfort clients report on bench.
On a row, cue the finish instead: pull to the ribs, hold the blades together for a count of one, then lower. Three sets of 10 with a genuine one-second hold beats four sets of 12 yanked.