Long ago SEO simply meant you tried to optimize your web site for search engines. These days various people offer this service to businesses, and their implementation is far from simple optimization -- they cheat. They run around the web, inserting text in forums and other accessible areas, sometimes creating web sites, all to increase the number of links to a web site. It is absurd. It is cheating. Those who do such things should keep in mind that it may very well backfire at some point and you'll be penalized for it. Further, it just isn't nice. I mean, when a user types something into Google, they aren't looking for whoever paid the most money to have an army of SEO 'professionals' run around the web spamming forums. They are looking for the best true organic result.
So, my advice to businesses: Forget this modern mutation of SEO. It certainly makes your business look bad. Usually it doesn't do that much good anyway, and may even back-fire on you.