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.
You can use this export to CSV function as a way to backup your data outside of Airtable.
If you're having issues with characters rendering incorrectly while importing your CSVs into other spreadsheet programs (either when using non-Latin characters or the extended Latin character set), see this article for instructions on how to fix the problem.