A map is almost universally a two-dimensional representation of a piece of three-dimensional space. Only with the advent of modern computer graphics were three-dimensional maps made possible.
Every map has a scale, determining how large objects on the map are in relation to their actual size. A larger scale shows more detail, thus requiring a larger map to show the same area.
If the map covers a large area of the earth surface, it also has a projection, a way of translating the three-dimensional real surface of the globe to a two-dimensional picture. The most commonly used is the Mercator Projection; other popular projections are polar and a variety of equal-area projections.
Maps covering parts of the earth tend to be either political or geographical. The most important purpose of the political map is to show national borders, and the purpose of the geographical is to show features of physical geography. Geological maps show not only the physical surface, but characteristics of the underlying rock, fault lines, and subsurface structures.
Because maps are abstract representations of the world they are not neutral documents and must be carefully interpreted.
In First person shooters and other computer games "map" refers to the current territory (including buildings, entities, spawn points, etc.) as well as the objectives that must be completed. For example, the map "de_dust" in Counter-strike includes the brushes, textures, bomb sites, spawn points, and backgrounds.