Search engine optimization copywriting is easier explained as "writing for the search engines". Copywriting is not merely placing words anywhere on a page and loading it with keyword phrases in attempt to rank well. SEO copywriting is an acquired skill that takes experience and knowledge to perform. SEO copywriting is one very competent method of achieving high and stable rankings within search engines. Search engines require text in order to classify a webpage's content within its directory. These keyword phrases must be represented within specific places in a webpage to ensure it meets the search engine standards. Over emphasising a particular phrase (spamming) can lead a search engine to steer clear of your website or penalize you for your efforts.
SEO copywriting has realistically three main goals. The first is to solely gain a high ranking for non-competitive keyword phrases. "You can read more on competitive key phrases within search engine optimization" The second is to assist and stabilise rankings for competitive keyword phrases. "Targeting competitive keyword phrases requires more than just good copywriting" The third is to achieve broad results that do well across many engines, taking into consideration that no one page will do equally well in all engines. You will always achieve the third goal, utilising quality copywriting techniques in conjunction with other proven optimization methods..
By no means is any method of optimization guaranteed to permanently hold a position. Even the very best search engine optimization copywriting will slip in rankings eventually, as other websites optimize to outperform current ranked websites. The end achievement with quality copywriting is to maintain rankings for a solid duration, often a year or two, within the free listings. The end result is traffic converted to sales for very little financial outlay compared to other marketing or advertising methods.
All optimization methods have advantages and disadvantages. Copywriting is not for every website. Not every website can hold several hundred words upon a page due to the design. Copywriting has its place and a professional SEO will inform you if its right for you.
Want to read more? Another informative source is an article by Phil Craven on Search Engine Optimization Copywriting.