Upon looking under the list of posts I flagged, some are pending/ helpful. Under those helpful ones, some are highlighted in red. What does that mean?
If by "highlighted in red" you mean a pink background behind the question title,
then that indicates that the post in question has been deleted.
If you mean something else, then you should provide a screenshot and be more descriptive about the circumstances (type of flag raised, whether it was on a question/answer/comment, etc.).
$\begingroup$ Yes! Thanks a lot!!! $\endgroup$ Jan 3, 2018 at 14:52
2$\begingroup$ @XcoderX The request nevertheless still holds: please be a good deal more specific when using this meta as a help resource. $\endgroup$ Jan 3, 2018 at 14:54
$\begingroup$ Okay noted @EmilioPisanty $\endgroup$ Jan 3, 2018 at 14:55