SEM (Search Engine Marketing) provides immediate website visibility through paid campaigns. It focuses on a larger number of keywords than SEO work. Where SEO aims to provide better organic search results, SEM uses search engines to advertise a website to Internet consumers. For each identified keyword there is an associated CPC (cost per click), you can set a daily budget. It is a variable cost, it is possible to turn web marketing campaigns on and off at any time, however once the budget has been used up you stop being visible; therefore it is a tool to be used with care, always keeping an eye on the costs incurred.