How to Create a CSV File to Download using Magento 2?

In Magento 2 Native, One php class \Magento\Framework\App\Response\Http\FileFactory is used for create csv and download CSV by magento way. create() function in FileFactory.php is used for create CSV file.
There are many another way to download CSV file using Core PHP script but its not best way to use within Magento Coding standard.
You can write CSV and download a CSV file using just simple below code snippet in your controller file,

When you run controller action you can download CSV file using just Magento straight forward way.
Using the above way you can download CSV file using Magento 2 Way.