What is a KMZ file?

A KMZ file is essentially a zipped version of a Keyhole Markup Language (KML) file. KML is an XML-based format used for representing geographic data in a way that can be displayed on Earth browsers, such as Google Earth. The primary purpose of compressing a KML file into a KMZ format is to reduce file size, which makes it easier to share and download, especially when the KML file contains multiple resources such as images or icons.

By zipping the KML file and its associated resources into a KMZ file, users can conveniently package all related data into a single file, streamlining the transfer and use of geographic information. This format is widely used in GIS applications and for mapping projects.

The other options do not accurately represent the function of a KMZ file; it is not about encryption, it does not define a new version of KML, nor is it inherently a type of vector file. The distinction of KMZ as a compressed KML file is fundamental to its utility in GIS applications, making it the correct answer.