The term for people who enjoy
railways,
trains and all related material. Also known as
trainspotters, these people are most often (but not limited to)
middle-aged men. Some may even be existing or retired rail employees who just love the magic of railways. A whole industry of
cab view videos and magazines exists for these people.
Quite often they will have an encyclopaedic knowledge of locomotives, rolling stock, signal operations, route layouts, operating procedures, and would probably be capable of driving a real locomotive given the chance.
In recent years, with the adventure of mass market train simulator software, railfans across the world are finally realizing their dream of both driving trains and recreating their favourite routes. Correspondingly, the number of train crews being pestered by fans to get pictures of the inside of cabs and recordings of the train must be skyrocketing as they rush to perfectly duplicate their local services into a simulator.
I have a bit of railfan in me thanks to my father, although one of my uncles was a textbook railfan, having devoted an entire room in the small B&B in Devonshire he ran to his train items, ranging from models and maps to home-made videos shot on holiday whilst riding, of all places, on the footplate of a locomotive in India.
Generally railfans are salt of the earth, decent, honest, hardworking types, although some would say those who sit on the platform with cameras and sound recording equipment take it a bit far (see also: saddos, spods, need to get out more). Draw your own conclusions.