What is .htaccess file?
.htaccess file is a plain text powerful file that controls high-level configuration of your website. On servers that run Apache (Apache is a web server software), the .htaccess file allows you to make changes to your website’s configuration without having to edit the server configuration files.
On Apache software the .htaccess files are hidden because this files have important configuration information and can compromise your server capability.
The .htaccess file is commonly located in the public_html folder on web server.
If you don't see your .htaccess file in your public_html folde, you may have to check "Show hidden files". You can access your .htaccess file from your hosting account's file management like "file manager" in cPanel or Plesk.
There are several use cases for the .htaccess file such as add redirect rule for certain file or directory, load custom error pages, force www or https instead of http, password-protect certaind directories, prevent hotlinking, block or allow ips or bad bots, to add Caching shema for certain file extensions ad so on.
You can apply different settings to different directories on your server by using multiple .htaccess files. You can, theoretically, create a .htaccess file in any directory on your server by creating and uploading a plain text file.