home_url() and site_url() in WordPress is very simple thing, but could be little bit confusing. Look at the image, then I described below –
From Setting -> General
1) WordPress Address (URL) = site_url()
2) Site Address (URL) = home_url( )
You could force rewrite that from wp-config.php too. Remembering is easy, its just opposite to what is says, so in Setting “Site Address (URL)” is home_url not the site_url as it looks from the words. Savvy?