Underwire bras are a type of women's lingerie designed to provide support and shape to the breasts. They feature a thin, flexible wire sewn into the fabric beneath each cup, which helps lift and separate the breasts for a more defined silhouette. This design can enhance comfort and improve the fit of clothing. These bras come in various styles, including push-up, sports, and full-coverage options, catering to different preferences and occasions. While many women appreciate the added support, it's essential to choose the right size and style to ensure comfort and avoid potential discomfort from the underwire.