Isobars are lines on a weather map that represent areas with equal atmospheric pressure. Each isobar line follows a path through locations with an equal atmospheric pressure that is plus or minus four starting with 1000 millibars.
Isobars represent adjusted atmospheric pressure. This removes pressure discrepancies caused by the location's relation to sea level or altitude. Isobars are also adjusted when necessary so that they never cross or touch. Weather maps with isobars give pressure information at a glance. They also give an approximation of wind direction because wind moves from high-pressure areas to low-pressure areas as large air masses move through the pressure differential.