What does the red flagging mean with Yahoo email?

i noticed a piece of email can be flagged. but i never really used it. what does it do? what's it's purpose?

What does the red flagging mean with Yahoo email?
to mark important email making returning to it easier
Reply:Its just a way to visually mark the importance of a message. A sort of reminder that a message may important or it may be something you need to follow up on.
Reply:it means that if u like or say want 2 keep ur best of the best of emails in ur noticed era , u can have that in ur ''red flagging''
Reply:To notify the user that the e-mail is high priority.
Reply:I seen that but never knew what it met