A Bartholin's cyst is a fluid-filled sac that forms in one of the Bartholin glands, which are located on either side of the vaginal opening. These glands produce lubrication for the vagina, and when their ducts become blocked, fluid can accumulate, leading to the formation of a cyst. Bartholin's cysts are usually painless and may not require treatment unless they become infected or cause discomfort. In such cases, a healthcare provider may recommend drainage or other interventions to relieve symptoms and prevent recurrence.