Files with a KMZ file extension are usually zipped or compressed KML files. KML stands for Keyhole Mark-up Language and files associated with this technology are usually used by geo-browser programs like Google Earth or Blender in importing geographical data. KML files then contain geographical data and its associated resources and when this file is zipped, the extension becomes KMZ.
KMZ files can be opened using a typical archiving utility or decompression tool. A regular KMZ file will contain one or more KML documents. KML documents are XML-based illustration of data which can be overlaid on 2D or 3D maps. This data will include but is not limited to longitude and latitude basis for geographical locations, points, lines and even text that will be useful in describing a location, and paths or links to external images and/or 3D textured objects which can also illustrate a geographic location. These information or resources are typically distributed in several KML files and in several folders within a KMZ file.
KMZ files are usually self-contained, which means that users can be assured that all required resource or files are packaged together in the KMZ file and that even the folder structure therein is retained. Thus, a KMZ file is an ideal format to manage KML files and distribute this kind of data anywhere. Since KMZ files are compressed, it is also smaller in size compared to the raw KML files and so it is much better to distribute and transfer even in a network with bandwidth issues. KMZ files can also be directly decompressed by applications that support the KML file extension, so an unzipping utility is not really necessary. But if a user changes the file extension from KMZ to ZIP, he can extract the contents of the file using any archiving tool like WinZip, WinRAR and many more.
Below are the geographic applications that support KML and KMZ files:
ESRI ArcGIS Desktop