Where do trains refuel?

Electric trains (and electrically powered locomotives) do not need to refuel. Or you could say they are constantly fuelling themselves from the electric supply.

Diesel trains and diesel locomotives are refuelled either at depots at the start or end of the working day, or at fuelling points at stations as necessary.

Steam locomotives (which these days are only used on tourist nostalgia services) are fuelled with coal, and re-supplied with water, at depots and stations. This has to be done a lot more frequently than with diesels.