A Keyword Salience score is used in SEO to quantify the importance or relevance of a keyword on a particular page.

Based on the salience score, we are able to understand which keywords are most closely associated with a piece of content. We can then determine whether or not we ought to try and naturally integrate our chosen keywords even more into the text.

If the salience score is lower than 0.02, we recommend incorporating the keyword into the content even more.

If the salience score is above 0.02, it generally means that the keyword is associated enough with the page. Therefore, it's a good start in helping Google to identify what your page topic is about.