What is KML and KMZ?
KML stands for Keyhole Markup Language and is a variant of simple XML.
KMZ is the compressed archive version of KML. It contains at least one KML file but can also contain many other ancillary files like images or HTML. KMZ files make KML smaller in size and more portable.
Keyhole was purchased by Google and is the company that originally developed the core software product now known as Google Earth. Internally, Google Earth uses an optimized streaming format that allows for very large amounts of data to be retrieved and then displayed on your computer. However, the developers wanted to allow for runtime customizations of the display so they also added the KML syntax for both end users and developers to use.
Arc2Earth will convert vector and raster data into KML/KMZ formats.