The 500 internal server error is a common web server error. It is not specific to WordPress and can happen with any website.
The 500 in the error message is technically an HTTP error code. Looking up this code will only show its standard description:
“500 Internal Server Error response code indicates that the server encountered an unexpected condition that prevented it from fulfilling the request.“
This is a generic catch-all error message, which means that the server was unable to assign a better, more helpful error message when it encountered the issue.
The error page looks different depending on which web server software (Nginx or Apache) your website uses and which browser you use.
Here is how the Apache error page may look:
This is how to fix the error using .htaccess
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress