A GMAP file is a map created by Google Drive, a a web application suite that allows you to create, edit, share, and store files. It does not store the document itself, but instead contains a reference to the document online in the Google My Maps tool. GMAP files include the URL of the document, the document ID, and the user's email address.
After installing the Google Drive desktop client, your Google Drive files, which may include GMAP, .GDOC, .GDRAW, .GSLIDES, and .GTABLE, are accessible within a special folder named Google Drive. This folder is located on the local hard drive and is used to synchronize files with the remote Google Drive on the web.
When you save a map in My Maps, a GMAP file is created in your Google Drive folder. The file functions similar to a .URL Internet shortcut file that, once double-clicked, opens the file in Google Drive in your default browser.
The My Maps tool is acccessible in Google Drive. It allows you to create maps, draw lines, shapes, or place marks, style your content with different colors and icons, and organize maps into different layers. You can also import geographic data such as place names, addresses, and coordinates from .CSV, .XLSX, .KML, and .GPX files.
NOTE: In 2018, the Google Drive desktop applications were discontinued but you can still access Google Drive online.