In the past, the name Holland was used to refer to the entire country, but this was largely due to the fact that North Holland and South Holland were the most economically and culturally powerful regions. It's a bit like how New York City is often used as a synonym for the entire state of New York, when in fact there's so much more to the state than just the city.
So, why does it matter? Well, for one thing, the Dutch people themselves make a distinction between the two terms. If you're visiting the southern province of Limburg, for example, you might get some curious looks if you refer to the entire country as Holland. It's not a huge deal, but using the correct term can show that you're interested in learning about the local culture.
Another cool thing to note is that The Netherlands is home to a wide range of dialects and regional identities. Just as the Southern United States has its own unique culture and way of speaking, different parts of The Netherlands have their own distinct flavors. From the Frisian language spoken in the north to the Brabantian dialect spoken in the south, there's a rich tapestry of linguistic and cultural diversity to explore.
Holland vs Netherlands: What's the Difference? (+ Map) | ViaTravelers