This is the 371st most frequent French word.
belge
Belgian.
Here, 'belge' modifies the noun 'chocolat', indicating the origin of the chocolate as being from Belgium.
Le chocolat belge est réputé dans le monde entier.
Belgian chocolate is renowned worldwide.
In this statement, 'belges' is the plural form of the adjective 'belge', agreeing with the plural noun 'amis' (friends).
Nous avons rencontré des amis belges lors de notre voyage.
We met Belgian friends during our trip.
In this sentence, 'belge' is used as an adjective to describe Marie's nationality, and since 'Marie' is feminine, it matches her gender.