A globe is a three-dimensional object that accurately depicts the geometry of the Earth, while a flat map is a two-dimensional representation that has some distortions. Although globes are more accurate, maps are easier to use.
The Earth is a spherical object, and since a globe shares the same shape, it can accurately depict the scale of continents and oceans. However, globes present a number of inconveniences for daily use. For example, it is difficult to measure distances on a globe's curved surface. Unlike globes, maps are versatile, depicting all or part of the Earth's surface at different scales on a surface that is easy to transport and view.
Map projections represent the curved surface of the Earth on a flat 2-D surface. There are several different map projections, but one of the most common is the Mercator, first invented in 1568. This projection distorts the size of the continents as it depicts the equator and the poles at equal widths. However, it is an excellent choice for navigation because it has straight rhumb lines.
Other projections distort different aspects of the Earth, such as shape, distance or direction. Maps may be classified based on the type of distortion present. For example, maps that show accurate relative sizes are "equal area" projections while those that depict accurate distances are "equidistant" projections. Projections like the Lambert Azimuthal Equal-Area projection maintain accurate directions and are used for maps, such as aeronautical charts, where directions are important.