Postcard from Amsterdam
Have a look at the people on the card, and their different clothing styles.
The real "star" on this card is of course the beautiful tram. Trams were a major mode of transport at the time, not only in the city but also to connect different towns. The tram is still important for Amterdam and several other major cities, but outside the main cities the tram has disappeared completely.
The tram on the card is an electric tram, getting electricity from the wires overhead (the trams in use today still work the same way). The electric tram was introduced in Amsterdam in 1900, so it was still quite new when this card was sent in 1904 - possibly the recipients of this card never saw one. Other trams in use at the time include steam trams and horse-drawn trams.