Standard Dutch (Standaardnederlands or Algemeen Beschaafd Nederlands — ABN) is the variety taught in schools and used in media. It is most associated with the Randstad (the urban area including Amsterdam, Rotterdam, The Hague, and Utrecht). When you learn Dutch from a textbook or app, this is what you learn. However, regional accents and dialects vary enormously across the country.
Northern accents: Gronings speakers have a distinct melody and some unique vocabulary. Fries (Frisian) is a separate language spoken in Friesland — not a Dutch dialect, but a co-official language with its own grammar and vocabulary. These northern varieties sound quite different from Randstad Dutch. Southern accents: Noord-Brabant has a softer, more singing quality and Flemish-influenced sounds. Limburg has the most distinct accent — Limburgs is sometimes classified as its own language, with tones that have no parallel in standard Dutch.
For language learners: start with standard Dutch from educational resources. Once comfortable, expose yourself to regional variation through Dutch television series set in different regions (Flikken Maastricht for Limburg, De Brug for border areas). Understand that native speakers will recognise your non-native accent and not expect regional naturalness from you. The most important distinction to master early: the Flemish Dutch of Belgium versus Netherlands Dutch — they share vocabulary but have significant pronunciation and idiomatic differences.