You export all of the records in a given grid view to CSV by clicking the view menu button (...) and then selecting the "Download CSV" menu option. This functionality is only available on our web and desktop applications.
You can use this export to CSV function as a way to backup your data outside of Airtable and into another program (like Excel or Google Sheets). When you download the CSV file, it will be located in your devices default download location (more info on finding this is available here for Macs, and here for Windows)