Search engine optimization is a combination of on-page and off-page services that help naturally promote your website up in search engine results by utilizing quality tactics approved of by the search engine industry.
Areas of a successful SEO campaign will include content development, keyword and market research, online exposure assistance, earned backlinking opportunities, coding enhanced and mobile responsive website adjustments, page load speedup, growing website depth, growing page depth, social media exposure, local profile setup or enhancements, 3rd party website listings, PPC campaigns and article writing and submission.
In a nutshell, there is no single area of improvement but rather an extensive list of areas that all makeup the algorithm for successfully boosting your website with search results and page rank.
Optimizing your website for search engines such as Google or Bing will help improve where these search engines place your website on their search results pages for keywords and phrases people use when searching for products or services with similarity to yours.
In order to determine a websites keywords, overall quality and indexability, search engines deploy special computers and software to crawl and index your website to check over its coding and on-page content.
Having missing or improperly coded pages, low page/keyword content or overused keyword content can drastically affect your websites ability to list well on search results. Beyond this, having a professional review and adjust various aspects of your website also helps boost your visitor to client conversions as well as helping to lower your bounce rates.
In the end, all the above factors add up to additional website visitors and increased sales or client conversions for your business.