Routing vs use of htaccess???

[eluser]123wesweat[/eluser]
Hi,

i am having some difficulties with Wordpress and CI and i came across this

Because both wordpress and codeigniter handle their redirects through
php and not apache, apache has no way of knowing if a particular URL
was handled correctly by either, so apache rules don’t really count
here.

And i was wondering what the relationship is between CI routing and the use of htaccess??

1/Does the router library overrides htaccess settings.
2/ Or does the router library "sees" what the mod rewrite rule was??

Any info, tips??