Flat maps of the world look distorted when compared to a globe due to the difficulties of representing three-dimensional objects in two dimensions. Map projections are different ways of representing the various continents, but each provides its own distortion depending on the technique it uses.
The easiest way to visualize the problem with map projections is to imagine removing the skin of an orange in one piece and attempting to press it flat. The resulting surface is not a perfect rectangle, which is how most maps are depicted. In order to make the skin form a rectangle, some areas must be stretched, causing a distortion in the surface. In a map of the world, this causes land masses near the poles to seem much larger than they actually are.
One common method of trying to correct a two-dimensional map is by expanding the equatorial region. This creates a map with bulging, round sides, and the north-south lines of longitude are no longer parallel but follow this curve. While this projection may provide a better representation of the size of the continents, it can make it difficult to understand their spatial relations with one another due to the distortion of cardinal directions. The only display that preserves the size, orientation and relative position of the continents requires a three-dimensional sphere.