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. The perfect keyword density will help achieve higher search engine positions. Consider the optimum keyword density to be 2 to 5 percent. Using high density of keyword could be considered as spam.
Keyword Cloud is a visual depiction of keywords used on a website, keywords having higer density are depicted in a larger fonts. Ideally your main keywords should appear in larger fonts at the start of the cloud.
A tag cloud or keyword cloud is a visual representation for text data, typically used to depict keyword metadata (tags) on websites, or to visualize free form text. 'Tags' are usually single words, normally listed alphabetically, and the importance of each tag is shown with font size or color. This format is useful for quickly perceiving the most prominent terms and for locating a term alphabetically to determine its relative prominence. When used as website navigation aids, the terms are hyperlinked to items associated with the tag. Credit: http://en.wikipedia.org/wiki/Keyword_Cloud
Keyword stuffing is considered to be an unethical search engine optimization (SEO) technique. Keyword stuffing occurs when a web page is loaded with keywords in the meta tags or in content.
