Why does a website redirect to another website?

What are the reasons that a website like http://www.example.com/ would redirect to http://www.example.com/foo/? Why is the homepage not actually hosted on the home page, from a design perspective?

• When running some SEO checks on one of our sites, I noticed that this page does a 302 redirect to the /foo page.  It's not even like the rest of the site lives on /foo/*; only a few other folders are on there. I'm no expert, but I know 302 redirects are not SEO friendly, and that all the incoming links to http://example.com are losing the majority of their link juice. Still, it is one of our best ranking pages- does that mean if we fix this redirect, rankings should get even better?

• Answer:

  It could be a redirect directive or rewrite rule left over from when the site was being developed (maybe people were previewing the new design under "foo" on the live server, then they put in this redirect as an easy way to cut over -- just a guess). Places to look include httpd.conf and .htaccess files. In general it's not a good idea to have a noise word in the URL, so you should lose the "foo" by removing the broken rule or setting up a new rule.  Then do a proper 301 redirect from "/foo" to the real home page. Yes, your home page should do better in rankings when this is fixed.