Why do we sometimes refer to the country of Holland and other times refer to the same place as the Netherlands? The correct name is Netherlands, or rather the Kingdom of the Netherlands, although it is informally known as Holland for historical reasons. Holland used to be a political region of the Holy Roman Empire called the County of Holland. Later, the province of Holland, as part of the Dutch Republic, rose to become a maritime and economic power, overshadowing the other provinces. Today, the Netherlands consists of twelve provinces, two of which are called North Holland and South Holland and occupy roughly the same territory as the old County of Holland. These two important provinces hold the three largest cities of the Netherlands, Amsterdam, Rotterdam and The Hague.
So call it what you want, everyone will understand you. But if the situation demands academic exactitude, call it the Netherlands.