This flag should be checked for articles that have some content that is not completely filled out. You should also mark the specific content that is incomplete using the associated Editorial block. Note that there are more specific flags for incompleteness in some areas, like examples, compatibility tables, etc.
TODO: Links to the other related flags
Manual of Style
TODO: Figure out which piece of Manual of Style this relates to
Once all sections have all of the relevant content as defined in the WPD/Manual_Of_Style you may remove this flag.
Be sure to mark which content is outdated using the associated editorial block: Template:Editorial/Content_Incomplete.
The editorial block should be as close to the incomplete content as possible. If that’s not possible (for example because the outdated is in a rigidly-structured part of the page), then put it in the Editorial Block at the top of the page.
If most of the content is incomplete, the editorial block should go in the Editorial Blocks section at the top of the page.