Google Earth KMZ/KML
Google Earth can be downloaded for free from Google. For more information about KML and KMZ format files please see the Google Developer introduction or the Google Earth outreach content. To open a KML or KMZ file in Google Earth, save the file to your PC and then double click the file. Google Earth will start automatically and load the new content. Alternatively you can add the file through Google earth by selecting file and then open and then selecting the correct KML or KMZ file. KML Files can be read by several GIS tools including ArcGIS, QGIS and the free ESRI viewer ArcGIS Explorer Desktop.
Google Earth is a free to use Geographic Information System that can be used to view spatial information in a variety of formats. Spatial data can be provided as Keyhole Markup Language (KML) and in a compressed format (KMZ). These files can be read by Google Earth and numerous other GIS platforms.