When I first started web development ten years ago, there weren't many websites yet. I still remember when the first few commercials mentioning a .com address started appearing on television. Nowadays, it seems every company has a website and a lot of individuals have one or more as well. That's a whole lot of content for the search engines to index.
Since the web is available to the masses, more businesses are using it in addition to, or even instead of, print ads to get their marketing materials in front of the public. In the early days of the web, you simply filled out a form and submitted your site for the search engine spiders to index. As the web grew, the search engines started using better technology to rank and display relvant sites. In response, marketing departments are clamoring to improve search engine placement.
Companies specializing in SEO (search engine optimization) can help drive targeted traffic to the appropriate website. They are also key to helping understand the various rules and workarounds for increasing page ranking. In a web world this large, it's a job better left to the pros.