This META tag was designed specifically with search engines in mind. It provides the search engine with the description that is displayed when your site is included in the search engine results. This is important. Since this is usually what your potential website visitor sees on the search engine, be sure that you use attention getting headlines in 15 words or less. This is where you define this.
Most search engines place additional emphasis on words contained in the web pages title.
Be sure to include a couple of your top keywords in a brief phrase.