It is the search engines that finally brings your website into the view of your prospective customers. That alone shows the inherent value of search. Now, when a topic is typed for search, nearly instantly, the search engine will sift through millions of pages it has indexed and present you with the ones that it believes best matches your topic. The searched results are also ranked, so that the most relevant ones come up first.
Remember that a prospective customer will probably only look at the first 2-3 listings in the search results, sometimes the whole first page. So it does matter where your website appears in the search engine ranking and you should be paying attention to where you are ranked and listed.
Further, prospective customers will almost all use one of the top 3-5 search engines. You want to be listed high in these search engines so you can attract more visitors to your website(s). Much of all SEO work depends on which search engines the customers use and how those engines value your site. Keeping track of when and what updates are happening in any search engine’s algorithms will help keep your website listed where you want it.
Keywords play an important role, more than any expensive online or offline advertising of your website. All search engines employ a ranking algorithm and one of the main rules in a ranking algorithm is to check the location and frequency of keywords on a web page. Don’t forget that algorithms also give weight to link population (number of web pages linking to your site). When performed by a qualified, experienced search engine optimization consultant, boosting your site high in search engine rankings really does happen.
With better knowledge of search engines and how they work, you can also do it on your own. This is often called In House SEO.