This is a white middle square, and its reduced version is
▫️ white small square and
◽️ white middle small square, its enlarged version is
⬜️ large white square. On the Internet, people use it as a white color card, or as a decorative symbol for text content. When it appears with
◼️ black squares, we think of mosaics. Related emojis：
⚫️ black circles,
⚪️ white circles.