SEM is the acronym for Search Engine Marketing and though it is often confused with SEO (Search Engine Optimization), it is not the same thing. SEM is the specific part of online marketing that can be the most effective and achieve almost instant results. Search Engine Marketing is based on PPC (Pay-per-click) advertising through search engines; allowing you to receive great results when people search for a product or service that you offer. As with all advertising, Pay-per-click campaigns cost money, and depending on the keywords, can cost several thousand dollars per month.