What is search engine optimization?

Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via "natural" ("organic" or "algorithmic") search results.

 
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What is search engine marketing?
Search engine marketing, or SEM, is a form of Internet marketing that seeks to promote websites by increasing their visibility in search engine result pages (SERPs).

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Why SEO is very important in SEM?
Search Engine Marketing (SEM) - Search Engine Optimization (SEO) is important to your business ...

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