Google Earth was released in June, 2005, but the story of it begins well before that. Keyhole, Inc was formed in 2001 and created a product called “Earth Viewer” — essentially an early version of what we now know as Google Earth.
Google purchased Keyhole in 2004 and released it to us a year later. Between Google’s influence and the new low price of free (none of Keyhole’s products were completely free), Google Earth instantly become a huge hit.
Keyhole developed a whole new world for us to dive into, and one aspect of that was the “KML” file — Keyhole Markup Language. It works similarly to standard XML files, but has a variety of special components specifically for geo-related stuff. KML is what allowed me to start projects such as Google Earth Hacks, where users have uploaded nearly 30,000 KML files. We also include KML files with many of our posts on here to help provide a quick link to view a particular item in Google Earth
If you’re a developer and you’re interested in learning more about KML, Google has a great section of KML Documentation to help you get started.
You’ll also encounter a “KMZ” file from time to time. This is a zipped file that contains a KML along with other media (usually images). If you need to open it to examine the contents, just rename it from “file.kmz” to “file.zip” and it’ll unzip the same way as any other compressed file.