A vital application of Google Earth includes Layers, which can be summarized as a collection of data points with geographic referencing. The data points can be anything the creator of a layer so chooses. Speaking of layer creators, anybody can be a layer creator! All layers are assembled in a Keyhole Markup Language (KML, for short) file format, which can be created by those with knowledge of the language and computer science. The KML file will then be processed as a layer when downloaded by Google Earth, with geo-referenced data provided with such great visual appeal!
Google Earth provides many layers pre-downloaded in its software, including Weather, 3D Buildings, and many more provided in the Earth Gallery button on the Google Earth Home Page. And aside from the layers available in Google Earth, there are multiple downloadable KML files from the internet that reach across all disciplines, from meteorology to environmental science, and even literature!
While these layers are an aesthetically pleasing manner to present data, layers are also extremely user-friendly. Once a layer is downloaded and processed by Google Earth, users have a multitude of options. Some layers provide geographical data that have tags which can be clicked to elicit more data. Some layers include polygons of data that cover a geographic area. Other layers may include time lapses of data, valuable for historical presentations. A layer is only limited by the extent of the KML file, and from there, the layer can “cover” what you want.