This flag is used to mark pages that have content that should be split into multiple articles. In practice this may because a single article has grown too large to suitably cover a single topic.
Manual of Style
TODO: Develop which section of Manual of Style this is related to.
If an article has this flag, first think what other article should be created. Then create that article and start splitting up the content.
If you check off this flag you should include a Template:Editorial/Split_Candidate template in the body.