If you have limited range of motion in overhead activities or feel like your pec muscles or lats may be tight, this stretch is a great way to target the fibers you rarely stretch in your chest. Often we stretch the pec muscles through horizontal abduction (regular pec stretch), and we neglect the rest of the functions of the pec major. The sternocostal head of the pec major (lower pec) plays a role in extension of the arm, this can cause it to limit overhead range of motion in combination with the lat.
You can stretch both individually through various forms of lat stretches or lower pec stretchs that put the shoulder into flexion to elongate the lower pec fiber. However a great way to integrate both muscles into a stretch and make sure everything is in line is by doing the hanging stretch. This is done by (obviously hanging) placing the hands either shoulder width or a little wider whichever is comfortable for you, and allowing yourself to hang down.
Once in that position you can relax your shoulder blades and them come up, this will bring the insertions of the muscles even further giving you a better stretch. Try to relax completely if the intensity is too high for you, you can try partially hanging by supporting yourself with your legs. Or lastly you can use a resistance bad (rogue band) attached over head to pull your arm overhead and stretch the muscles.