Flag for review means the officials of something are checking to see if something is appropriate or not.

I assume this is from a social media website of some type (YouTube, instagram, tiktok, even possibly italki, etc.). If it was from a different context, then it could mean something slightly different. “Flag” means “tagged” “alerted” “pulled to the side” “For review” means someone is going to read it later “Flag for review” probably means that the community rules of the website were broken, and the website might delete it.

To "flag" something can mean to attach something to the edge of a page to make it easy to find. The flag might be a little piece of red sticky paper. It sticks out from a pile of sheets like a tiny red flag on the edge. More generally, it means to mark a place in a document to call attention to it. To "flag for review" means to mark it so that someone else can see the places that they need to check. Suppose you have 100-page legal document. Most of it looks right. There are one or two things you aren't sure about. You want somebody else to check them. "Flag for review" means to mark those places. They don't need to check all 100 pages. They only need to check the places flagged for review.

To "flag" something means to place a marker or placeholder, or to highlight. That means to "highlight or mark" something that needs to be reviewed at a later date.

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