You have to have an .htaccess file, it's called URL re-write, an example .htaccess file:
Options +FollowSymlinks
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !^/index.php
RewriteCond %{REQUEST_URI} (/|\.php|\.html|\.htm|\.feed|\.pdf|\.raw|/[^.]*)$ [NC]
RewriteRule (.*) index.php?query=$1&%{QUERY_STRING}
This will send everything like art/id/title to your index.php page and will be usable using $_GET['query']. So in the index.php file, you can use the variable like so:
echo $_GET['query'];