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Hi Emma, I feel your frustration. Unfortunately, we don't know all the ways in which Google's algorythm works, although we have a pretty good idea of many pieces of the puzzle. Even the highest correlated metric we know of, PageAuthority, only has a correlation of about 0.35 (1.00 being a perfect correlation). Pretty good for SEO, but in the real world it's not the best correlation. So the factors in the keyword difficulty tool are known ranking influences, but it's impossible to incorporate all 200+ ranking signals (some known, some unknown) into a single tool. Instead, the best way to use the tool is to use it to try to find out exactly why a page ranks above another. Is it over-optimized? What is it about those social signals that help? Are the links from relevant sources? Has the site been penalized? Yeah, it's conflicting and confusing. In truth, the first 80% of all SEO is pretty standard: Create good content, make sure it's accessible by Search Engines, Follow best SEO practices, market it smartly, get links, repeat. Do this well and you'll win most of your battles. The remaining 20% gets hard, and if we think about it too much, we sometimes waste our time. Regardless, the best strategy, in my opinion, is not to go after 1 keyword, but 100s at a time using a long-tail strategy. I wrote about it in more detail here: http://moz.com/blog/how-to-rank   If you're just starting out, or even experienced, it's the best way to go.