Web address of some web sites end with ".aspx", ".php", ".jsp", etc.How web developers can hide the extensions from visibility.

You can do this by using a rewrite module. For asp.net, its the URL Rewrite Module (or you can write a custom one), for php you'd use a .htaccess file with the rewrite rules, etc...

I thik for this you have to use .htaccessfil with some code in that.
here is exmple of php extensioncode:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^.]+)$ $1.php [NC,L]

First, confirm that the mod_rewrite component is set up. Then, be cautious to comprehend how it performs, many individuals get it in reverse.
You don't cover up web addresses or additions. What you do is make a NEW url that guides to the old one, for example
The URL to put on your website will be yoursite.com/play?m=asdf
or better yet
Even though the listing asdf does not are available. Then with mod_rewrite set up you put this in .htaccess. Generally it says, if the asked for URL is NOT a computer file and is NOT a listing, immediate it to my script