Primary keywords are the ones that are given the most significance while optimizing a web page. They mostly use on the areas like the header, footer, etc. Keywords are considered as primary because those are the ones that are marketable online and have a niche market.
Secondary keywords are less important and supports the primary keywords for its marketing and they are a lot of times combination of one or more keywords, it can be used with or without more combinations at different places.
A primary keyword, as the name suggests, is a keyword that is used before any other keywords on a web page or in an article. Therefore, the primary keyword is the most important keyword on a web page. The primary keyword should be included in a site’s title and domain as well as in its content. It should be added to the first sentence on the page too. The primary keyword is essential for purposes of SEO as it is used to describe the web page as well as help people locate the site.
Secondary keywords mean those keywords which play supporting role on the website. When a secondary keyword is used, the chances of attracting additional visitors to your site are increased.