At Admin -> Settings -> Switches, you have the option to allow CSV downloads of topics. If you enable this, your site's visitors will have the option to download a CSV file of all your topics which they can open in Excel, LibreOffice Calc or any other spreadsheet program. By default, the CSV download link appears in the member home area. You can use the code <a href="index.php?action=downloadcsv">Download CSV</a> to display it anywhere.

To select which fields to include or to download a CSV as an administrator, you can just use Admin Panel -> Miscellaneous -> Export CSV. This does not require the switch to be on.