Look at almost any world map on a classroom wall and Greenland sprawls across the top like a continent in its own right, looking every bit as massive as Africa. So most of us filed it away that way: Greenland, enormous. It is a perfectly reasonable thing to believe when the map says it to your face for twelve years of school.
Greenland covers about 2.2 million square kilometres. Africa covers about 30 million. Africa is roughly fourteen times larger, and you could drop Greenland into it with room for most of Europe besides. The distortion comes from the Mercator projection, the classic map design from 1569 built for ship navigation, which stretches everything near the poles to keep compass lines straight. The closer to the poles, the more inflated, so Greenland, Antarctica, Canada, and Russia all balloon, while equatorial Africa and South America get visually robbed. Flattening a sphere onto paper always lies somewhere; Mercator just chose to lie about size. Pull up a true-scale comparison once and you cannot unsee it. The map you trusted was drawn to help sailors, not to tell you how big anything is.