"Media" means middle. A reporter observes something and reports it to his employer. The employer decides to publicize it, so a news reader reads the story on a tv show, or a printer prints the story in a newspaper. You hear or read the story. Everything between the observation and you is in the middle, so any part of it, or the entire process, is called "media".
In printing, paper and ink are "media". In photography, all the equipment used to bring a scene to your eyes is called "media". On any highway, the line in the middle of the road is called "median". Median is singular and media is plural.