Follicles are localized areas of lymphoid hyperplasia that appear as white or gray elevations in the upper or lower tarsal conjunctiva and may be accompanied by inflammation. Papillae are flat-topped elevations in the tarsal conjunctiva containing blood vessels and having a smooth, velvety appearance, present in some forms of allergic conjunctivitis. The document distinguishes between follicles and papillae, defining each term and noting when they may be present.