Conformal projections preserve the property of shape over small areas. Conformal projections are used because they preserve directions around any given point. Additionally, relationships of the angles within the graticule can be shown correctly. Area and shape are normally distorted. Because of GIS emphasis on area portrayal, GIS systems often use conformal projections.
Some projections only preserve correct distance relationships along a few places on the map.
For example, an Equidistant azimuthal projection has the distance to the outside of the map portrayed correctly. A final category is compromise maps. They may be the average of two or more projections or interrupted or broken in order to minimize distortion. A conformal projection. Lambert Equal Area.