Ratings allow you to see if an article is helpful or not and should be rewritten, improved, or discarded entirely.
Each article is able to be rated once per user.
Find the article in the control panel.
Next look on the top right section of the page to see the article ratings.
Helpful - hand pointing up
Unhelpful - hand pointing down
An article is helpful for customers if it has high number of helpful ratings and a low number of unhelpful ratings.
If your article has more unhelpful ratings than helpful then you may consider rewriting it entirely.