An "htaccess" file is a configuration file read and used by the Apache web server to configure settings local to your website or even just a subdirectory in the website. These are local settings as opposed to what you would configure in .conf files in Apache's conf directory.
There should be a dot in the filename: .htaccess - and so the file will often be hidden or invisible in directory listings unless you specify that hidden or system files should appear. But the file should exist in any Drupal installation in the top-most directory of Drupal (next to the README and...