A map feature is a component of a map that helps to provide information about the area being mapped. An INSET is a smaller map within a larger map, usually used to show a different area in more detail. A SCALE is a set of numbers or lines used to measure distances on a map. A KEY is a set of symbols used to represent features on a map. A LEGEND is a chart that explains the symbols used on a map. An isobar is a line on a map connecting points of equal barometric pressure.