If you see “Holland” in a published source, like a book or an online tree, chances are that the person means the country of the Netherlands.
If you see “Holland” in a Dutch record prior to 1840, Holland refers to the province by that name, in the west of the Netherlands. In 1840, the province was split into Noord-Holland and Zuid-Holland.
As the most prosperous province and the center of international trade, the province overshadowed the other provinces; so much so that its name became synonymous with the country. Kind of like people calling Great-Britain “England.”
Next time you find a source that says your ancestor is from “Holland,” check if they meant the province or the country, so you know where to look.