Yes, there indeed is a difference. Holland is not the Netherlands. But why do people know Holland but have almost never heard of the Netherlands?
The Netherlands is the actual name of the country. Although people often refer to it as Holland because Holland has been, and still is, the buzzing west of the Netherlands. The Netherlands are divided into 12 provinces. The most known are North and South Holland. People often muddle them up and Holland becomes the name of the country instead.
History gives us another good reason. In the time of William of Orange and Philip the second, we see that William of Orange, also referred to as William the Silent, was not exactly on good terms with Philip the second. William inherited lands from his cousin. These lands are now known as the Netherlands and Belgium, but at that time they were called the Low Lands. Many different cultures lived there. When Philip got cross with William, William made Amsterdam his base of operations because he knew the area very well. At that time, the Low Lands were in the middle of revolution against the Catholic Church. Philip sent an army to the Low Lands to regain control. William united the people living in the Low Lands under the name of the Dutch Republic and reigned from the province of Holland. Eventually the Republic won the war and became independent with Amsterdam as its capital.
In the 17th century, which is the golden age for the Netherlands, ships of the Republic were seen all over the world. Whenever people asked where the captain of the ship was from, they would answer with the name of their province. This was almost always Holland. But things went sour for the Republic. The only important province was Holland. Holland took care of almost half of the income of the country. On top of that, the Republic was at war with England, France and the German Bishoprics. This year, 1672, is known as Rampjaar (Disaster Year).
Later on, the Netherlands was conquered by Napoleon and became part of France as a unitary state.
It was in the time of Napoleon that North and South Holland were born. Napoleon shaped the Netherlands and split Holland into two separate parts. These parts were reunited after Napoleon’s defeat but Holland was given two governors instead of one. And so, the Netherlands were divided as both governors did what was best for their respective part of Holland. And so, the people decided to split Holland back into two, South and North Holland.
Holland is indicated in red.
To sum it all up, Holland is a part of the Netherlands and consists of two parts. Holland was historically and economically the most known but that does not make all people in the Netherlands someone from Holland. So, people from Holland are part of the Dutch people who live in the Netherlands and not all Dutch people from the Netherlands are from Holland.