If you found questions something like Spam, Duplicate, off topic, not constructive, not a real question, etc you can flag it.
If you found answers like Spam, not an answer, etc you can flag it.
If you found comments like rude or offensive, not constructive / off-topic, obsolete, too chatty, etc you can flag it
Moderators and reviewers will look at the issue and decide whether the flag was helpful or not and mark it 'helpful' or 'declined' or 'disputed'.
You can earn badges like
Deputy - Raised 80 helpful flags
Marshal - Raised 500 helpful flags