The term 'TRAINS OVERHEAD' can be summarized by the three letter acronym ELS, which stands for Electric Locomotive System. This system is used to power trains that run on overhead electric lines. It is a type of traction system that uses electricity to provide power to the locomotives, allowing them to move along the tracks. The ELS system is used in many countries around the world and is a popular choice for railway operators due to its efficiency and cost-effectiveness.