The ? emoji, also known as the "100" emoji, is commonly used to indicate that something is perfect or excellent. It can be used to show agreement or emphasize a point, as in "I agree with you 100%." It can also be used to indicate a score of 100 out of 100, such as in a test or rating system. The emoji's popularity and versatility have made it a favorite among social media users, particularly on platforms like Twitter and Instagram.