See Netherlands for the country.
Holland is the western part of the Netherlands bordering the North Sea. At present Holland is divided into two provinces, North Holland and South Holland. The cities of Rotterdam, The Hague and Leiden are in South Holland, while Amsterdam, Haarlem and Alkmaar are in North Holland. Historically, Holland was the economically strongest part of the Netherlands (and it still is to this day), which is why the name Holland is often used to refer to the whole country (compare this with England and the United Kingdom or Great Britain and the United Kingdom).