Keyword rich content means that your website textual content should have as many of the keywords that you believe people will search for when searching for your product or service. This text should be “rich” with your keywords in context to what you are providing.
Do NOT put “hidden” text in your pages. This means text that is near to or the same color as the page color. Search engines, if this is found, will dump your site from their archives and it can be challenging to get re-listed.