Why does any URL like *page.html/**** open?

Question

htaccess

I don’t understand why when adding any sign at the end of the page address, after ".html" and "/" the page opens, instead of giving 404? What is wrong with htaccess?
Example: add /555
to the URL http://zabor-24.ru/profnastil/ekolux.html, but the page still opens as http://zabor-24.ru/profnastil/ekolux.html
zabor-24.ru/profnastil/ekolux.html/555 - it works!
Why is that?

#########################
AddDefaultCharset UTF-8
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.zabor-24.ru
RewriteRule (.*) http://zabor-24.ru/$1 [R=301,L]
AddHandler application/x-httpd-php .php .html
Action php5.4-script  /cgi-bin/php5.4.cgi
AddType php5.4-script .php
ErrorDocument 404 /404.html

Why does any URL like page page.html/* open?

Answer 1

Well, that's how the web works.
For example, here is the url of your question - https://toster.ru/q/359536
It is also available at the following addresses:

https://toster.ru/q/359536/
https://toster.ru/q/359536/vopros
https://toster.ru/q/359536/vopros/otvet/

If you do not make special efforts - everything will work by default.
And if you make an extra effort, then there is another option to complete urls - a question mark:
https://toster.ru/q/359536?vopros-otvet