Dutch is spoken in the Netherlands and in Belgium (where it is called Vlaams — Flemish). While the written standard is largely the same, pronunciation differences are significant. The most immediately audible: the g sound. Belgian Dutch typically has a soft, voiced g — more like the French r or a gentle voiced fricative. Netherlands Dutch (especially the north) has the hard, voiceless g. This alone makes speakers instantly identifiable by region.
Other pronunciation differences: the ij/ei sound is often realised differently — Belgian Dutch tends to keep it higher and tenser. The word stress pattern can differ slightly in some words. Belgian Dutch often sounds more melodic and slower to Netherlands Dutch ears — Belgians sometimes call Netherlands Dutch hard or sharp, while Dutch people find Flemish warmer or more musical. Neither is more correct — they are regional standards.
For learners, the practical advice: choose one variety to learn first, use consistent resources, and be aware that content from Belgium (VRT television, Flemish YouTube) will have the Flemish soft g. If you move to Belgium, adopt Flemish pronunciation for the g to sound natural locally. If in the Netherlands, use the hard g. You will understand both varieties after enough exposure — the vocabulary and grammar differences are minor compared to the pronunciation differences. The most significant vocabulary differences: Flemish uses gsm (mobile phone) where Dutch uses mobieltje, and Flemish frak (horrible) vs Dutch vies (dirty).