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