Meaning
A small red triangle pointing upward. It means up or increase, and its red colour also gives it a hint of alert.
People use it for rising prices, growing numbers and upward trends, or simply as a pointed bullet: “Gold price 🔺 again today” It can also point at the message above. Colour conventions differ, though: on Vietnamese stock boards red usually marks a fall, so 🔺 for gains can confuse some readers.