Which keyword is better?

I have talked about authors' having their own website. Even Better Keywords [download] from SearchGuild is a handy free Windows program that can help you find which keyword or phrase is more popular with searchers. For instance is science fiction more popular than scifi. or is film more popular than movie? It can also suggest other phrases that mean the same but might be easier to target on search engines.

enter some keywords and watch as the utility scans overture to get alternatives and then uses AlltheWeb to calculate how attractive the resultant phrases are in terms of SEO

How is this important? It might be vital in getting search engine traffic to your website.