Value:
'Contains stop words' indicates the presence of support words such as "and, for, on, the, etc.", which are largely ignored by the major search engines. While they do have some effect on search engine results, they are not given the same weight as standard nouns and verbs.

Recommendation:
Since they are often ignored, use of stop words is not recommended. They dilute the keyword density of your more important keywords and should be avoided if possible.