Keyword research is a technique that search engine optimization professionals use to find and research the actual search terms people type into search engines when searching for services, products & information. Search engine optimization professionals research keywords and keyword phrases to achieve higher rankings for their desired keywords & keyword phrases.
SEO's want to find the most effective and profitable keywords & phrases for your website. Long tail keyword phrases are important to many if not most websites. 70% of all internet searches are users searching with long tail search phrases.
Long tail keyword phrases would be "Hudson Valley NY house painters" instead of "painter" or "house painter". Almost all of the time these long tail keyword phrases have much lower competition and are easier to optimize for.
A good seo will try to find the most profitable keyword phrases. The lower the competition and the higher the search volume, the more valuable the keyword phrase is to your website.
KEI or keyword effectiveness is one of the most popular ways to score the effectiveness of a keyword or keyword phrase. The higher the KEI score, the more traffic search engines will deliver to your website. Basically The KEI of a key word is figured out by the ratio of the square of the searches upon a particular keyword in a day divided by the number of websites that are listed for that keyword. For example, a keyword that has 100 searches a day and for which Google shows 5000 websites would have a KEI of 2. (100 * 100 / 5000)