What is the difference between Holland and The Netherlands?

The Kingdom of the Netherlands is a state that consists of the country called the Netherlands as well as overseas territories in the Caribbean (Aruba, Curaçao, and Sint Maarten). 

The country of the Netherlands consists of twelve provinces; including North Holland and South Holland. 

Even though the name Holland is frequently used (sometimes even by the Dutch themselves) to refer to the whole country, it is only a part of it.