It's a marketing company:
Actually, it's a "search engine optimization" company: a company that provides business owners who haven't the time or wit to learn html and css (or hire someone competent who knows them) with services like adding appropriate meta tags, useful outbound links, alternate text for images, and other things that improve the page rank of pages on relevant searches.
I run a web page for my church and a web page for my wife's psychology practice and in both cases got high page ranks on relevant searches without engaging such a company. Somewhat amusingly, I get offers of SEO services for my church webpage, which shows up first or second on every search engine in all relevant searches I've tried. I briefly point this out to the offering company, telling them their services are not needed.