Underwear or swim briefs. The swimming variety are often called 'Speedos' after the brand. This emoji is shown in different colors and styles across platforms. Some platforms depict this emoji as tighty whities with a visible fly, while others use a less specific design.
Related emojis include 👙 Bikini, 🩳 Shorts, and 🩱 One-Piece Swimsuit.
📅 Briefs was approved as part of Unicode 12.0 in 2019
and added to Emoji 12.0 in 2019.