Welcome to the Search Engine Optimization Bible. Search engine optimization has come to mean a lot of things to a lot of different people. In the strictest sense, SEO is about the on-page and off-page design strategies you can use to improve your search engine ranking. This usually means tweaking your web site, using design elements and content. And in most cases, it also means spending no money at all. SEM, or Search Engine Marketing, is not just SEO. More accurately, SEM includes PPC or pay-perclick advertising. Search engine marketing is about doing whatever you need to do to ensure that your web site ranks as high as possible in search engine results. This means not only that you make the needed changes to your web-site design, but that you also employ other tactics, like using a paid advertising program or investing in content strategies.