Search engine optimizing is a process that optimizes your website in order for it to rank higher in search results. It also helps you get more organic traffic.
SEO is a history that dates back to the 1990s when search engines first appeared. SEO has become a key marketing strategy and is a rapidly growing industry.
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SEO and PPC are not part of search engine optimization. Search engine optimization only focuses on organic results. Search Engine Marketing includes PPC as well as SEO.