Keyword density is the percentage of times a keyword or phrase appears on a web page compared to the total number of words on the page. In the context of search engine optimization keyword density can be used as a factor in determining whether a web page is relevant to a specified keyword or keyword phrase. 

Keyword research is the process of determining what keywords are used in search engines by potential customers. 

There goals of keyword research include the following: 

  --Identify the broadest possible set of keywords used by potential customers. 
  --Determine which keywords are most popular and thus represent the primary targets for SEO and keyword advertising.
  --Identify keywords whose search engine ranking is realistically obtainable by SEO.
  --Determine what negative keywords will make keyword advertising most cost effective.
  --Identify customer language that can influence branding and messaging.
  --Develop additional content based upon user terminology.
  --Keyword research is a vital first step for successful search engine marketing campaigns.