Different purposes. Your annual gyn exam is your yearly well woman exam. You will undergo a pelvic exam with or without a pap, a breast exam, and be offered std screening depending on your age/risk factors. Your postpartum exam occurs approximately 6 weeks after your baby is born. Its purpose is to make sure that your vagina has healed, your body has returned to normal, and to discuss future contraceptive plans.
Annual exam is once. A yr where a breast and pelvic and if you are over a certain age, i start at 40, a rectal exam is done, a post partum exam is usually done 6 weeks after delivery to make sure everything is back to normal, you may or may not get a pap done at that exam , some obs do, some wait till one yr from your pap if your previous pap was normal.