The operation of modern trains depends on electricity to generate kinetic energy, and the role of wires on the train track is to transmit electricity to trains.
The first train was a steam train, powered by steam. Later, the train improved and began to rely on fuel to drive the train, so there were no wires on the train at that time. However, with the development of science and technology, the use of electricity is everywhere, and trains have developed to use electricity as power.
That's why there are wires on the train track. In fact, the electricity used by trains is the same as that used in our daily life, which is transmitted from the public power grid. The wire on the train track is the channel for the power grid to transmit power to the train, just like the data cable we use when charging our mobile phones.