What are "plain clothes"?

Plain clothes generally refer to everyday clothing that are simple, without any elaborate design or adornment. These clothes are typically comfortable and functional rather than fashionable or decorative. Plain clothes can include items such as t-shirts, jeans, and sneakers, as well as other practical items that people wear in their day-to-day lives. This term is often used in contrast to dressy or formal clothing, which is typically worn for special occasions or events. Plain clothes can be worn by anyone, regardless of gender or age, and are often chosen for their practicality and ease of wear.