Chunk  

Vanguard: Saga of Heroes Wikibase™ Dictionary

In Vanguard, a Chunk is a square section of the world map. Moving from one Chunk to another is often accompanied by a momentary lag, or hesitation, referred to as chunking, while Vanguard retrieves textures needed in the new Chunk. Obviously on slower computers or on systems with a slower or fragmented hard drive this can take a more noticeable time.

It is identified by it's map grid coordinates, in the form of east-west, north-south. So Hathor Zhi (-15,-10) is 1 chunk south of Lomshir (-15,-9).