A sty is a small, painful lump that forms on the eyelid, usually caused by a bacterial infection in the oil glands. It appears red and swollen, resembling a pimple, and can make the eye feel tender or irritated. Styes can occur on the outer or inner part of the eyelid and are often accompanied by symptoms like tearing or sensitivity to light. Most styes resolve on their own within a week or so. Applying warm compresses can help relieve discomfort and promote healing. If a sty persists or worsens, it is advisable to consult a healthcare professional for further evaluation and treatment options.