SEO (search engine optimization) could be defined as a series of actions done on website pages, in order to achieve better position on search engines, using keywords.
When ordering web pages, a client probably doesn't even think about web browsers optimization, mostly because of their ignorance, and it is most likely that they actually need SEO. Of course, it is not enough to put web pages on a server and expect that time does the work.
Ten years ago, it might have been working, but not today. Web pages are not just nice design and quality content. Today, web pages are a weapon to win a job over the Internet, to earn money, to work, to live, but also, to succeed.
Because of all of that, it is very important to introduce a client with the notion of SEO, how time consuming it is, what is important about it and, at the end, how it is going to be useful for your client's and yours budget. A good optimized web page can earn your client a great money so it is important that persons who work the optimization are well paid.
A great deal of owners of websites consider that it is enough just to type in URL of their website in address bar and that the first position on that kind of result list is good and enough.
SEO optimization represents adapting web site to search engines for keywords that are relevant for your products/services from a client perspective. Potential client will type in a search engine a certain word, for a desired product and based on it, links will appear for sites that offer those kinds of products.
If your web site doesn't have SEO done,it won't show as a search results for typed keywords in search engines. It's called ranking. For good positioning on the first Google page for certain keywords perfect SEO is necessary, as well as valid code and site updating.