A GSLIDES file contains a link to a presentation created by Google Slides, an online presentation editor included with Google Drive. It does not store the actual presentation, instead, it stores a URL reference to a Google Slides presentation in Google Drive.
GSLIDES file open in Google Slides (Google Drive)
Google Drive is a cloud-based service that provides file storage and several productivity apps, including the Docs, Sheets, and Slides programs. The Google Slides interface appears similar to Microsoft PowerPoint with a toolbar that allows you to insert text, images, shapes, tables, charts, animations, images, and Word art. You can also change the background, layout, theme, and transitions in the presentation.
Before 2018, the Drive productivity apps could be downloaded and installed in Windows or macOS. The GSLIDES files were accessible within a special folder named Google Drive on the local hard drive. This folder was used to synchronize files with the remote Google Drive.
Users could double-click a GSLIDES file to open the presentation in the Slides app in Drive in their default web browser. This functionality is similar to clicking an .LNK shortcut file in Windows or a .WEBSITE or .WEBLOC file to open a webpage in Internet Explorer or Chrome.
However, the Google Drive desktop applications were discontinued in 2018 and GSLIDES files are no longer used by Google Drive to store links to presentations in Slides. Users can still create presentations in Slides online in Google Drive.