Target high traffic keywords, get a good rank for those keywords, which will get you a nice amount of visitors , helping you sell your product & make money
because the keyword is the medium of the site from the visitors... it helps the visitors visit to your site through...
yea, the keywords are super important for making money if you are tying to sell a product, or just trying to receive highly targeted (and therefore very efficient and valuable) traffic to your site.
Yes keyword research is the most important steps, infact that is the first steps you must do. So that you can identified which keyword that is the most profitable. Choose a keyword that has low R/s (Results/Searches) ratio. Personally I choose R/S less than 10. You can use free keyword tools https://adwords.google.com/select/KeywordToolExternal or through my website here http://www.ivonson.com/tools
when you're on top at the SE with the keyword that means the product you sell, you get visitors that are interested in it
the more good the keyword,the more high the traffic you'll get,because people search something in search engine based on keyword,and the more traffic you'll get,the more earnings you'll have
if you refer to adsense earning then it can said that each keywords phrase has its value. popular keywords that related to high priced products could have high top bid. one adsense click for high paying keywords could go as high as USD50 dollars. but i believe high paying ads is only shown in established sites with high volume of traffic.