blog url and site url

There are two urls that we can set in the options. the site url and the blog url. here is what i think they are – and i have been wrong before

for blogs the site will be

<blog url>/posts

for pages like about page

<site url>/about

if this is true, in the function get_page_link() the link is created by

$link = get_settings('home') . "/$link/";

shouldnt that be

$link = get_settings('siteurl') . "/$link/";

and if my assumptions are wrong what is the difference