The areola is the pigmented region surrounding the nipple of the breast. Within the areola, there are sebaceous glands, sweat glands and modified mammary glands (glands of Montgomery). These glands produce small elevations on the areola surface. The sebaceous glands enlarge during pregnancy and secrete an oily material which acts as a lubricant for breastfeeding.
For more information, see Anatomy of the Breast.