I found this in wikipedia, I had also the same ambiguity :

" Holland is a region in the western part of the Netherlands. A maritime and economic power in the 17th century, Holland today consists of the Dutch provinces of North Holland and South Holland.
Usage :
The proper name of the area in both Dutch and English is "Holland". "Holland" is a part of the Netherlands. "Holland" is informally and quite incorrectly used in English and other languages, including sometimes the Dutch language itself, to mean the whole of the modern country of the Netherlands (this example of pars pro toto or synecdoche is similar to the tendency to refer to the United Kingdom as "England").

The people of Holland are referred to as "Hollanders" in both Dutch and English. Today this refers specifically to people from the current provinces of North Holland and South Holland. Strictly speaking, the term "Hollanders" does not refer to people from the other provinces in the Netherlands, but colloquially "Hollanders" is sometimes mistakenly used in this wider sense. "

The Netherlands :
"The Netherlands (Dutch: Nederland )) is the European part of the Kingdom of the Netherlands, which consists of the Netherlands, the Netherlands Antilles and Aruba in the Caribbean. The Netherlands is a parliamentary democratic constitutional monarchy, located in Western Europe. It is bordered by the North Sea to the north and west, Belgium to the south, and Germany to the east.

The Netherlands is often called Holland, which is formally incorrect as North and South Holland are merely two of its twelve provinces. For more on this issue see terminology of the Netherlands. The word Dutch is used to refer to the people, the language, and anything indigenous to the Netherlands."

I hope this help you to distinguish ;-)
I'd like if a Dutch guy answers to the question, maybe there are others differences.