Please explain htaccess file

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . index.php

    SetEnv SEO_SUPPORT 1

I don’t understand, please explain

I found some articles myself:
http://www.cnblogs.com/hechun...

Reply content:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . index.php

    SetEnv SEO_SUPPORT 1

I don’t understand, please explain

I found some articles myself:
http://www.cnblogs.com/hechun...

If the file requested in the URL does not exist and the folder does not exist, redirect to index.php
If apache loads the mod_env module, set an environment variable SEO_SUPPORT

Generally write pseudo-static rules