.GDOC File

Google Docs is an online word processor included as part of the free, web-based Google Docs Editors suite offered by Google, which also includes: Google Sheets, Google Slides, Google Drawings, Google Forms, Google Sites and Google Keep. Google Docs is accessible via an internet browser as a web-based application and is also available as a mobile app on Android and iOS and as a desktop application on Google's Chrome OS.

Google Docs allows users to create and edit documents online while collaborating with other users in real-time. Edits are tracked by the user making the edit, with a revision history presenting changes.

File extension gdocis mainly related to Google Drive, a web service and used for links to a document saved using the Docs app for Google Drive.

A .gdoc file contains web link to a document created and saved in Google Drive. These files do not contain the actual document, just encoded URL link.

These files are typically found in your Google Drive folder that is synchronized with the service. Opening it results in launching Google Drive in your Web browser so you can edit the document.

Files with gdoc extension are URL links to a document created in Google Drive. It is not the actual document, just link. You can download the document from Google Drive in more typical format, like docx or odt.

Google Docs supports opening and saving documents in the standard OpenDocument format as well as in Rich text format, plain Unicode text, zipped HTML, and Microsoft Word. Exporting to PDF and EPUB formats are implemented.
How to open:
These files can only be opened using web browser and edited using Google Docs web app. It will launch the on-line word processor (Similar to Microsoft Word) in your web browser.
How to convert:
When you open the document in Google Drive or integrated Google Docs web app, you have the option to save it to another format using the File -> Download as function. Google Driver supports DOCX, ODT, RTF, PDF, TXT and HTML formats for output documents.