Prominence is how close to the start of the area that the keyword appears.
If a keyword appears at the beginning of an area, its prominence will be 100%.
If a keyword appears in the middle of an area, its prominence will be 50%.
So use your important keywords in the top of the web page when optimizing for search engines
Yes, keyword density. That's what I meant. The ratio of the keyword to the rest of the words/phrases in the content. How often the keyword is repeated within the content.
No, its not about keyword repetition. Keyword prominence refers to the position of the keywords in the text. If you use your keywords in the beginning of the sentences, the keyword prominence is higher. Higher keyword prominence is better.