The term 'Rail Heading' can be summarized as a four-letter word, 'MONO'. Rail Heading is a term used to describe the direction of a railway line. It is the angle at which the track is laid in relation to the geographic north. This angle is measured in degrees and is usually between 0 and 360. Rail Heading is important for railway engineers to consider when designing a railway line, as it affects the speed and safety of the train.